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  • CLASSES

    Other Urinary Antiseptics
    Urinary Analgesics and Anesthetics

    DEA CLASS

    Rx

    DESCRIPTION

    Combination product used to relieve symptoms of urinary irritation or urinary tract infection.

    COMMON BRAND NAMES

    Azuphen MB, Darcalma, Hyolev MB, MD 20, Phosenamine, Phosphasal, UR N-C, Uramit, Urelle, Uretron DS, Uribel, Urimar-T, Uro-L, Uro-MP, Ustell, UTA, UTICAP, Utira-C, Utrona-C

    HOW SUPPLIED

    Azuphen MB/Hyoscyamine Sulfate, Methenamine, Methylene Blue, Phenyl Salicylate, Sodium Phosphate, Monobasic/Phosenamine/Uramit/Uribel/Uro-MP/Ustell/UTA/UTICAP Oral Cap
    Darcalma/Hyolev MB/Hyoscyamine Sulfate, Methenamine, Methylene Blue, Phenyl Salicylate, Sodium Phosphate, Monobasic/MD 20/Phosphasal/UR N-C/Urelle/Uretron DS/Urimar-T/Uro-L/Utira-C/Utrona-C Oral Tab

    DOSAGE & INDICATIONS

    For the treatment of symptoms of irritative voiding including for the relief of local urinary symptoms such as inflammation, hypermotility, and mild pain, which accompany lower urinary tract infection (UTI); also for the relief of urinary tract symptoms caused by diagnostic procedures.
    Oral dosage
    Adults

    1 tablet/capsule PO 4 times per day with liberal fluid intake after each dose.

    Children > 6 years and Adolescents

    The manufacturer does not recommend a specific dosage and suggests that the dosage should be individualized by the prescriber.

    MAXIMUM DOSAGE

    Adults

    4 tablets/capsules per day PO.

    Elderly

    4 tablets/capsules per day PO.

    Adolescents

    Dosage not specified; do not exceed adult max of 4 tablets/capsules per day PO.

    Children

    > 6 years: Dosage not specified; do not exceed adult max of 4 tablets/capsules per day PO.
    <= 6 years: Use not recommended.

    Infants

    Use not recommended.

    Neonates

    Use not recommended.

    DOSING CONSIDERATIONS

    Hepatic Impairment

    Specific guidelines for dosage adjustments in hepatic impairment are not available. However, methenamine is contraindicated in patients with severe hepatic disease.

    Renal Impairment

    Specific guidelines for dosage adjustments in renal impairment are not available. However, methenamine is contraindicated in patients with severe renal insufficiency or severe dehydration. Also, methylene blue's primary route of elimination is via the kidneys.

    ADMINISTRATION

    Oral Administration

    Drink plenty of fluids after each dose.

    STORAGE

    Azuphen MB:
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Darcalma :
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Hyolev MB:
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    MD 20 :
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Phosenamine:
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Phosphasal:
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    UR N-C :
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Uramit :
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Urelle:
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Uretron DS:
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Uribel :
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Urimar-T:
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    Uro Blue:
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    Uro-L:
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Uro-MP:
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Ustell:
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    UTA:
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    UTICAP:
    - Protect from direct sunlight
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place
    Utira:
    - Store at room temperature (between 59 to 86 degrees F)
    Utira-C:
    - Store at controlled room temperature (between 68 and 77 degrees F)
    - Store in a cool, dry place
    Utrona:
    - Protect from moisture
    - Store at room temperature (between 59 to 86 degrees F)
    Utrona-C :
    - Store at room temperature (between 59 to 86 degrees F)
    - Store in a cool, dry place

    CONTRAINDICATIONS / PRECAUTIONS

    General Information

    NOTE: This monograph discusses the use of hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate combination products. Clinicians may wish to consult the individual monographs for more information about each agent.
     
    There have been no studies to establish the safety of prolonged use of hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate.

    Salicylate hypersensitivity

    Do not use hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate in any patient with a known hypersensitivity to any of the product components. Cross-sensitivity may occur in patients with known belladonna alkaloids hypersensitivity or salicylate hypersensitivity.

    Cardiac arrhythmias, cardiac disease, coronary artery disease, heart failure, mitral stenosis

    Hyoscyamine is an anticholinergic agent and can cause tachycardia. The manufacturer contraindicates the combination in patients with cardiac disease, including cardiac arrhythmias, heart failure, coronary artery disease, and mitral stenosis. The risk-benefit of hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate should be carefully considered. If rapid pulse, dizziness, or blurred vision occurs, discontinue use immediately.

    GI obstruction

    Hyoscyamine is an anticholinergic agent and can decrease gastrointestinal motility and gastric emptying. The manufacturer contraindicates the combination in patients with GI obstruction or GI obstructive disease. The risk-benefit of hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate should be carefully considered.

    Glaucoma

    Hyoscyamine is an anticholinergic agent and can increase intraocular pressure. The manufacturer contraindicates the combination in patients with glaucoma. The risk-benefit of hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate should be carefully considered as increased ocular pressure may precipitate an acute attack of glaucoma.

    Myasthenia gravis

    Hyoscyamine is an anticholinergic agent and may compete with acetylcholine in patients with myasthenia gravis. The manufacturer contraindicates the combination in patients with myasthenia gravis. The risk-benefit of hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate should be carefully considered.

    Prostatic hypertrophy, urinary retention, urinary tract obstruction

    Hyoscyamine is an anticholinergic agent. The manufacturer contraindicates the combination in patients with obstructive uropathy (urinary tract obstruction), such as bladder neck obstruction due to prostatic hypertrophy. The risk-benefit of hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate should be carefully considered as acute urinary retention may be precipitated.

    Dehydration, renal disease, renal failure, renal impairment

    Hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate should be used with caution in patients with severe renal impairment, renal disease, or renal failure as methenamine is contraindicated in patients with severe renal insufficiency or severe dehydration.

    Hepatic disease

    Hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate should be used with caution in patients with hepatic disease. Methenamine is contraindicated in patients with severe hepatic disease since intestinal production of ammonia could be exacerbated.

    MAOI therapy

    Methylene blue is a component of hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). Clinicians should be aware of a potentially fatal interaction between methylene blue and serotonergic agents such as selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), and clomipramine. MAO-A is responsible for the metabolism of serotonin; therefore, concurrent use of an MAO-A inhibitor with a serotonergic agent may result in a clinically significant interaction. Some case reports and other clinical data suggest that serotonin syndrome may occur post-operatively following administration of standard infusions of methylene blue to patients stabilized on an SSRI, SNRI, or clomipramine (see Interactions). In theory, methylene blue may also interact with monoamine oxidase inhibitors (MAOIs) or drugs that possess MAOI-like activity (e.g., furazolidone, isoniazid, procarbazine, linezolid); therefore, use of methylene blue during MAOI therapy should be avoided if possible. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma.

    Children, infants, neonates

    Hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate is indicated in children > 6 years and adolescents; however, no specific dosage is recommended by the manufacturer. Use in neonates, infants, and children <= 6 years is not recommended due to the potential toxic effects of belladona alkaloids (hyoscyamine).

    Pregnancy

    The manufacturer states that hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate is classified in pregnancy category C. Hyoscyamine and methenamine cross the placenta; however, no studies concerning effect on the fetus have been done. The manufacturer recommends that hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate should only be given if the benefit to the mother outweighs the risk to the fetus.

    Breast-feeding

    The manufacturer of hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate states that problems in humans have not been documented with breast-feeding. However, methenamine and traces of hyoscyamine are excreted in breast milk. In 4 women, a mean breast-milk concentration of 50 micromol/L was reported. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally ingested drug, healthcare providers are encouraged to report the adverse effect to the FDA.

    Geriatric

    Geriatric patients may be more susceptible to adverse events with normal doses of hyoscyamine; methenamine; methylene blue; phenyl salicylate; sodium biphosphate. Geriatric patients may respond to usual doses with excitability, agitation, drowsiness, or confusion due to the hyoscyamine component. According to the Beers Criteria, anti-spasmodics such as hyoscyamine are considered potentially inappropriate medications (PIMs) in geriatric patients and should be avoided in this population due to uncertain effectiveness and high anticholinergic activity. The Beers expert panel also recommends avoiding drugs with strong anticholinergic properties, such as hyoscyamine, in geriatric patients with the following disease states or symptoms due to the potential for exacerbation of the condition or increased risk of adverse effects: dementia/cognitive impairment (adverse CNS effects), delirium/high risk of delirium (possible new-onset or worsening delirium), or lower urinary tract symptoms/benign prostatic hyperplasia in men (possible urinary retention or hesitancy).

    ADVERSE REACTIONS

    Moderate

    sinus tachycardia / Rapid / Incidence not known
    confusion / Early / Incidence not known
    excitability / Early / Incidence not known
    blurred vision / Early / Incidence not known
    urinary retention / Early / Incidence not known
    dyspnea / Early / Incidence not known

    Mild

    flushing / Rapid / Incidence not known
    agitation / Early / Incidence not known
    drowsiness / Early / Incidence not known
    dizziness / Early / Incidence not known
    vomiting / Early / Incidence not known
    nausea / Early / Incidence not known
    xerostomia / Early / Incidence not known
    urine discoloration / Early / Incidence not known
    stool discoloration / Delayed / Incidence not known
    rash (unspecified) / Early / Incidence not known
    pruritus / Rapid / Incidence not known

    DRUG INTERACTIONS

    Acetaminophen; Aspirin, ASA; Caffeine: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic.
    Acetaminophen; Butalbital; Caffeine; Codeine: (Severe) Codeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of codeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as codeine. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when codeine is used concomitantly with an anticholinergic drug. The concomitant use of codeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Acetaminophen; Caffeine; Dihydrocodeine: (Severe) Dihydrocodeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of dihydrocodeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as dihydrocodeine. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when dihydrocodeine is used concomitantly with an anticholinergic drug. The concomitant use of dihydrocodeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Acetaminophen; Caffeine; Magnesium Salicylate; Phenyltoloxamine: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Acetaminophen; Caffeine; Phenyltoloxamine; Salicylamide: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; Phenylephrine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Acetaminophen; Chlorpheniramine; Phenylephrine; Phenyltoloxamine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Acetaminophen; Codeine: (Severe) Codeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of codeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as codeine. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when codeine is used concomitantly with an anticholinergic drug. The concomitant use of codeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Acetaminophen; Dextromethorphan: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Acetaminophen; Dextromethorphan; Doxylamine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Acetaminophen; Dextromethorphan; Guaifenesin; Phenylephrine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Acetaminophen; Dextromethorphan; Phenylephrine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Acetaminophen; Dextromethorphan; Pseudoephedrine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Acetaminophen; Diphenhydramine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Acetaminophen; Hydrocodone: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Acetaminophen; Oxycodone: (Major) Serotonin syndrome can occur during concomitant use of opiate agonists with serotonergic drugs, such as methylene blue. Symptoms may occur hours to days after concomitant use, particularly after dose increases. Serotonin syndrome may occur within recommended dose ranges. If concomitant treatment is clinically warranted, careful observation of the patient is advised, especially during initiation of the second therapy and after dosage increases of either agent. Instruct patients to immediately report symptoms of agitation, hallucinations, tachycardia, fever, excessive sweating, shivering or shaking, muscle twitching or stiffness, trouble with coordination, nausea, vomiting, or diarrhea. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when oxycodone is used concomitantly with an anticholinergic drug. The concomitant use of oxycodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Acetaminophen; Pentazocine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when pentazocine is used concomitantly with an anticholinergic drug. The concomitant use of pentazocine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) Theoretically, concurrent use of methylene blue and pentazocine may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and pentazocine increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Acetaminophen; Tramadol: (Severe) Tramadol use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of tramadol with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome or seizures. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as tramadol. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when tramadol is used concomitantly with an anticholinergic drug. The concomitant use of tramadol and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Acetazolamide: (Major) Avoid the coadministration of high-dose salicylates and carbonic anhydrase inhibitors whenever possible. There were reports of anorexia, tachypnea, lethargy, metabolic acidosis, coma, and death with high-dose aspirin and acetazolamide. Two mechanisms could cause increased acetazolamide concentrations, resulting in CNS depression and metabolic acidosis: first, competition with aspirin for renal tubular secretion and, second, displacement by salicylates from plasma protein binding sites. Additionally, carbonic anhydrase inhibitors alkalinize urine and increase the excretion of normal doses of salicylates; decreased plasma salicylate concentrations may or may not be clinically significant. (Major) The therapeutic action of methenamine requires an acidic urine. Acetazolamide can alkalinize the urine, thereby decreasing the effectiveness of methenamine. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended.
    Aclidinium: (Moderate) Although aclidinium is minimally absorbed into the systemic circulation after inhalation, there is the potential for aclidinium to have additive anticholinergic effects when administered with other anticholinergics or antimuscarinics.Per the manufaturer, avoid concomitant administration of aclidinium with other anticholinergic medications, when possible.
    Acrivastine; Pseudoephedrine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Albuterol; Ipratropium: (Moderate) Although ipratropium is minimally absorbed into the systemic circulation after inhalation, there is the potential for tiotropium to have additive anticholinergic effects when administered with other antimuscarinics. Per the manufaturer, avoid concomitant administration of ipratropium with other anticholinergic medications, such as antimucarinics.
    Alfentanil: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when alfentanil is used concomitantly with an anticholinergic drug. The concomitant use of alfentanil and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Aliskiren; Amlodipine; Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Aliskiren; Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Alkalinizing Agents: (Major) Avoid the administration of Alkalinizing agents to patients who are being treated with methenamine, as an acidic urine is required for methenamine therapeutic efficacy. Alkalinized urine decreases methenamine efficacy by increasing the amount of non-ionized drug available for renal tubular reabsorption and inhibits the conversion of methenamine to formaldehyde, which is the active bacteriostatic form.
    Alogliptin: (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Alogliptin; Metformin: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control. (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Alogliptin; Pioglitazone: (Moderate) Salicylates can indirectly increase insulin secretion. Thus, salicylates can decrease blood sugar. In large doses, salicylates can cause hyperglycemia and glycosuria. (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Alosetron: (Major) Concomitant use of alosetron and anticholinergics, which can decrease GI motility, may seriously worsen constipation, leading to events such as GI obstuction, impaction, or paralytic ileus. Although specific recommendations are not available from the manufacturer, it would be prudent to avoid anticholinergics in patients taking alosetron.
    Alpha-glucosidase Inhibitors: (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood sugar. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Aluminum Hydroxide: (Major) Aluminum hydroxide and magnesium hydroxide (as well as other antacids, i.e. aluminum hydroxide; magnesium carbonate, aluminum hydroxide; magaldrate; magnesium hydroxide, and aluminum hydroxide; magnesium trisilicate) may interact with urinary acidifiers by alkalinizing the urine. Frequent use of these high dose antacids should be avoided in patients receiving urinary acidifiers. (Major) The therapeutic action of methenamine requires an acidic urine. Antacids containing alkalinizing agents such as sodium bicarbonate can alkalinize the urine, thereby decreasing the effectiveness of methenamine by increasing the amount of non-ionized drug available for renal tubular reabsorption. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended. (Moderate) Antacids may inhibit the oral absorption of anticholinergics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction.
    Aluminum Hydroxide; Magnesium Carbonate: (Major) Aluminum hydroxide and magnesium hydroxide (as well as other antacids, i.e. aluminum hydroxide; magnesium carbonate, aluminum hydroxide; magaldrate; magnesium hydroxide, and aluminum hydroxide; magnesium trisilicate) may interact with urinary acidifiers by alkalinizing the urine. Frequent use of these high dose antacids should be avoided in patients receiving urinary acidifiers. (Major) The therapeutic action of methenamine requires an acidic urine. Antacids containing alkalinizing agents such as sodium bicarbonate can alkalinize the urine, thereby decreasing the effectiveness of methenamine by increasing the amount of non-ionized drug available for renal tubular reabsorption. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended. (Moderate) Antacids may inhibit the oral absorption of anticholinergics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction.
    Aluminum Hydroxide; Magnesium Hydroxide: (Major) Aluminum hydroxide and magnesium hydroxide (as well as other antacids, i.e. aluminum hydroxide; magnesium carbonate, aluminum hydroxide; magaldrate; magnesium hydroxide, and aluminum hydroxide; magnesium trisilicate) may interact with urinary acidifiers by alkalinizing the urine. Frequent use of these high dose antacids should be avoided in patients receiving urinary acidifiers. (Major) The therapeutic action of methenamine requires an acidic urine. Antacids containing alkalinizing agents such as sodium bicarbonate can alkalinize the urine, thereby decreasing the effectiveness of methenamine by increasing the amount of non-ionized drug available for renal tubular reabsorption. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended. (Moderate) Antacids may inhibit the oral absorption of anticholinergics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction.
    Aluminum Hydroxide; Magnesium Hydroxide; Simethicone: (Major) Aluminum hydroxide and magnesium hydroxide (as well as other antacids, i.e. aluminum hydroxide; magnesium carbonate, aluminum hydroxide; magaldrate; magnesium hydroxide, and aluminum hydroxide; magnesium trisilicate) may interact with urinary acidifiers by alkalinizing the urine. Frequent use of these high dose antacids should be avoided in patients receiving urinary acidifiers. (Major) The therapeutic action of methenamine requires an acidic urine. Antacids containing alkalinizing agents such as sodium bicarbonate can alkalinize the urine, thereby decreasing the effectiveness of methenamine by increasing the amount of non-ionized drug available for renal tubular reabsorption. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended. (Moderate) Antacids may inhibit the oral absorption of anticholinergics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction.
    Aluminum Hydroxide; Magnesium Trisilicate: (Major) Aluminum hydroxide and magnesium hydroxide (as well as other antacids, i.e. aluminum hydroxide; magnesium carbonate, aluminum hydroxide; magaldrate; magnesium hydroxide, and aluminum hydroxide; magnesium trisilicate) may interact with urinary acidifiers by alkalinizing the urine. Frequent use of these high dose antacids should be avoided in patients receiving urinary acidifiers. (Major) The therapeutic action of methenamine requires an acidic urine. Antacids containing alkalinizing agents such as sodium bicarbonate can alkalinize the urine, thereby decreasing the effectiveness of methenamine by increasing the amount of non-ionized drug available for renal tubular reabsorption. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended. (Moderate) Antacids may inhibit the oral absorption of anticholinergics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction.
    Amantadine: (Major) Additive anticholinergic effects may be seen when hyoscyamine is used concomitantly with other drugs that possess antimuscarinic effects.
    Ambenonium Chloride: (Major) The muscarinic actions of ambenonium chloride can antagonize the antimuscarinic actions of hyoscyamine.
    Amiloride: (Moderate) Salicylates can increase the risk of renal insufficiency in patients receiving diuretics, secondary to effects on renal blood flow. Salicylates inhibit renal prostaglandin production, which causes salt and water retention and decreased renal blood flow. This combination may cause hyperkalemia.
    Amiloride; Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal insufficiency in patients receiving diuretics, secondary to effects on renal blood flow. Salicylates inhibit renal prostaglandin production, which causes salt and water retention and decreased renal blood flow. This combination may cause hyperkalemia. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Aminoglycosides: (Minor) Due to the inhibition of renal prostaglandins by salicylates, concurrent use of salicylates and other nephrotoxic agents like the aminoglycosides may lead to additive nephrotoxicity.
    Amitriptyline: (Severe) Per the manufacturer, treatment initiation with amitriptyline is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than amitriptyline (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving amitriptyline and requiring urgent treatment with IV methylene blue, amitriptyline should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 2 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Amitriptyline may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent, in patients receiving serotonergic agents. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma.
    Amitriptyline; Chlordiazepoxide: (Severe) Per the manufacturer, treatment initiation with amitriptyline is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than amitriptyline (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving amitriptyline and requiring urgent treatment with IV methylene blue, amitriptyline should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 2 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Amitriptyline may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent, in patients receiving serotonergic agents. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma.
    Amlodipine; Benazepril: (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation.
    Amlodipine; Hydrochlorothiazide, HCTZ; Olmesartan: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Amlodipine; Hydrochlorothiazide, HCTZ; Valsartan: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Amoxapine: (Severe) According to the manufacturer, treatment initiation with amoxapine is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than amoxapine (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving amoxapine and requiring urgent treatment with IV methylene blue, amoxapine should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 2 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Amoxapine may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent, in patients receiving serotonergic agents. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma. (Moderate) Depending on the specific agent, additive anticholinergic effects may be seen when amoxapine is used concomitantly with other anticholinergic agents. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive CNS effects are also possible when these drugs are combined with amoxapine.
    Amphetamine: (Severe) Amphetamines should not be administered during or within 14 days after the use of methylene blue. Methylene blue is a potent, reversible monoamine oxidase inhibitor (MAOI) which can prolong and intensify the cardiac stimulation and vasopressor effects of amphetamines, potentially resulting in hypertensive crisis. Methylene blue also has the potential to interact with serotonergic agents, such as amphetamines, which may increase the risk for serotonin syndrome. Serotonin syndrome is characterized by mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea), and in rare instances, death. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents, such as amphetamines, with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma.
    Amphetamine; Dextroamphetamine Salts: (Major) Urinary acidifying agents, such as ammonium chloride, phosphorus salts, and methenamine salts (e.g., methenamine; sodium acid phosphate), reduce the tubular reabsorption of amphetamines. As a result, amphetamine clearance is accelerated and the duration of effect is reduced. Combination therapy should be avoided if possible.
    Amphetamine; Dextroamphetamine: (Severe) Amphetamines should not be administered during or within 14 days after the use of methylene blue. Methylene blue is a potent, reversible monoamine oxidase inhibitor (MAOI) which can prolong and intensify the cardiac stimulation and vasopressor effects of amphetamines, potentially resulting in hypertensive crisis. Methylene blue also has the potential to interact with serotonergic agents, such as amphetamines, which may increase the risk for serotonin syndrome. Serotonin syndrome is characterized by mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea), and in rare instances, death. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents, such as amphetamines, with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma.
    Amphetamines: (Severe) Amphetamines should not be administered during or within 14 days after the use of methylene blue. Methylene blue is a potent, reversible monoamine oxidase inhibitor (MAOI) which can prolong and intensify the cardiac stimulation and vasopressor effects of amphetamines, potentially resulting in hypertensive crisis. Methylene blue also has the potential to interact with serotonergic agents, such as amphetamines, which may increase the risk for serotonin syndrome. Serotonin syndrome is characterized by mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea), and in rare instances, death. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents, such as amphetamines, with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma.
    Amphotericin B cholesteryl sulfate complex (ABCD): (Minor) Concurrent use of amphotericin B and other potentially nephrotoxic medications, like the salicylates, may enhance the potential for drug-induced renal toxicity.
    Amphotericin B lipid complex (ABLC): (Minor) Concurrent use of amphotericin B and other potentially nephrotoxic medications, like the salicylates, may enhance the potential for drug-induced renal toxicity.
    Amphotericin B liposomal (LAmB): (Minor) Concurrent use of amphotericin B and other potentially nephrotoxic medications, like the salicylates, may enhance the potential for drug-induced renal toxicity.
    Amphotericin B: (Minor) Concurrent use of amphotericin B and other potentially nephrotoxic medications, like the salicylates, may enhance the potential for drug-induced renal toxicity.
    Angiotensin-converting enzyme inhibitors: (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation.
    Antacids: (Major) Aluminum hydroxide and magnesium hydroxide (as well as other antacids, i.e. aluminum hydroxide; magnesium carbonate, aluminum hydroxide; magaldrate; magnesium hydroxide, and aluminum hydroxide; magnesium trisilicate) may interact with urinary acidifiers by alkalinizing the urine. Frequent use of these high dose antacids should be avoided in patients receiving urinary acidifiers. (Major) The therapeutic action of methenamine requires an acidic urine. Antacids containing alkalinizing agents such as sodium bicarbonate can alkalinize the urine, thereby decreasing the effectiveness of methenamine by increasing the amount of non-ionized drug available for renal tubular reabsorption. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended. (Moderate) Antacids may inhibit the oral absorption of anticholinergics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction.
    Antithrombin III: (Moderate) Large doses of salicylates (more than 3 to 4 g/day) can cause hypoprothrombinemia, an additional risk factor for bleeding. Patients taking large doses of salicylates and antithrombin III should be monitored closely for bleeding.
    Antithymocyte Globulin: (Moderate) An increased risk of bleeding may occur when salicylates are used with agents that cause clinically significant thrombocytopenia due to decreases in platelet aggregation, such as anti-thymocyte immune globulin.
    Apixaban: (Major) Large doses of salicylates (>= 3-4 g/day) can cause hypoprothrombinemia, an additional risk factor for bleeding. Patients taking large doses of salicylates and apixaban should be monitored closely for bleeding.
    Ardeparin: (Moderate) An additive risk of bleeding may be seen in patients receiving a low molecular weight heparin in combination with other agents known to increase the risk of bleeding such as salicylates. Monitor clinical and laboratory response closely during concurrent use.
    Ascorbic Acid, Vitamin C: (Moderate) The therapeutic action of methenamine requires an acidic urine. Ascorbic acid, vitamin C can produce unpredictable changes in urine pH and should be avoided as a urinary acidifier. In addition, orange juice also should be avoided because citric acid ultimately may raise urine pH. (Minor) Agents that acidify the urine should be avoided in patients receiving high-dose salicylates. Urinary pH changes can decrease salicylate excretion. If the urine is acidic prior to administration of an acidifying agent, the interaction should be minimal.
    Aspirin, ASA: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic.
    Aspirin, ASA; Butalbital; Caffeine: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic.
    Aspirin, ASA; Butalbital; Caffeine; Codeine: (Severe) Codeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of codeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as codeine. (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when codeine is used concomitantly with an anticholinergic drug. The concomitant use of codeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Aspirin, ASA; Caffeine; Dihydrocodeine: (Severe) Dihydrocodeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of dihydrocodeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as dihydrocodeine. (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when dihydrocodeine is used concomitantly with an anticholinergic drug. The concomitant use of dihydrocodeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Aspirin, ASA; Carisoprodol: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic.
    Aspirin, ASA; Carisoprodol; Codeine: (Severe) Codeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of codeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as codeine. (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when codeine is used concomitantly with an anticholinergic drug. The concomitant use of codeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Aspirin, ASA; Dipyridamole: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic.
    Aspirin, ASA; Omeprazole: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic.
    Aspirin, ASA; Oxycodone: (Major) Serotonin syndrome can occur during concomitant use of opiate agonists with serotonergic drugs, such as methylene blue. Symptoms may occur hours to days after concomitant use, particularly after dose increases. Serotonin syndrome may occur within recommended dose ranges. If concomitant treatment is clinically warranted, careful observation of the patient is advised, especially during initiation of the second therapy and after dosage increases of either agent. Instruct patients to immediately report symptoms of agitation, hallucinations, tachycardia, fever, excessive sweating, shivering or shaking, muscle twitching or stiffness, trouble with coordination, nausea, vomiting, or diarrhea. (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when oxycodone is used concomitantly with an anticholinergic drug. The concomitant use of oxycodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Aspirin, ASA; Pravastatin: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic.
    Atenolol; Chlorthalidone: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Atropine; Difenoxin: (Moderate) Diphenoxylate is a synthetic opiate derivative that appears to exert its effect locally and centrally on the smooth mucle cells of the GI tract to inhibit GI motility and slow excess GI propulsion. The effects can be additive to antimuscarinic agents, such as hyoscyamine. In some cases, constipation might occur, and effects on the CNS or bladder function may also be additive.
    Atropine; Diphenoxylate: (Moderate) Diphenoxylate is a synthetic opiate derivative that appears to exert its effect locally and centrally on the smooth mucle cells of the GI tract to inhibit GI motility and slow excess GI propulsion. The effects can be additive to antimuscarinic agents, such as hyoscyamine. In some cases, constipation might occur, and effects on the CNS or bladder function may also be additive.
    Atropine; Edrophonium: (Major) The muscarinic actions of edrophonium chloride can antagonize the antimuscarinic actions of hyoscyamine.
    Azelastine; Fluticasone: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Azilsartan; Chlorthalidone: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Bacitracin: (Minor) Additive nephrotoxicity may occur with concurrent use of systemic bacitracin and other nephrotoxic agents, including salicylates. Topical administration of any preparation containing bacitracin, especially when applied to large surface areas, also should not be given with other drugs that have a nephrotoxic potential.
    Barbiturates: (Moderate) Due to high protein binding, salicylates could be displaced from binding sites, or could displace other highly protein-bound drugs such as barbiturates. An enhanced effect of the displaced drug may occur.
    Beclomethasone: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Belladonna Alkaloids; Ergotamine; Phenobarbital: (Moderate) Theoretically, concurrent use of methylene blue and ergot alkaloids may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and ergot alkaloids increase central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Belladonna; Opium: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when opium is used concomitantly with an anticholinergic drug. The concomitant use of opium and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Benazepril: (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation.
    Benazepril; Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Bendroflumethiazide; Nadolol: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Benzphetamine: (Severe) Amphetamines should not be administered during or within 14 days after the use of methylene blue. Methylene blue is a potent, reversible monoamine oxidase inhibitor (MAOI) which can prolong and intensify the cardiac stimulation and vasopressor effects of amphetamines, potentially resulting in hypertensive crisis. Methylene blue also has the potential to interact with serotonergic agents, such as amphetamines, which may increase the risk for serotonin syndrome. Serotonin syndrome is characterized by mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea), and in rare instances, death. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents, such as amphetamines, with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. (Major) Urinary acidifying agents, such as ammonium chloride, phosphorus salts, and methenamine salts (e.g., methenamine; sodium acid phosphate), reduce the tubular reabsorption of amphetamines. As a result, amphetamine clearance is accelerated and the duration of effect is reduced. Combination therapy should be avoided if possible.
    Betamethasone: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Bismuth Subsalicylate: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic.
    Bismuth Subsalicylate; Metronidazole; Tetracycline: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic.
    Bisoprolol; Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Botulinum Toxins: (Moderate) The use of systemic antimuscarinic/anticholinergic agents following the administration of botulinum toxins may result in a potentiation of systemic anticholinergic effects (e.g., blurred vision, dry mouth, constipation, or urinary retention).
    Bromocriptine: (Moderate) Bromocriptine is highly bound to serum proteins. Therefore, it may increase the unbound fraction of other highly protein-bound medications (e.g., salicylates), which may alter their effectiveness and risk for side effects. (Moderate) Theoretically, concurrent use of methylene blue and ergot alkaloid derivatives such as bromocriptine may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and ergot alkaloids increase central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Brompheniramine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Brompheniramine; Carbetapentane; Phenylephrine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including anticholinergics. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Brompheniramine; Dextromethorphan; Guaifenesin: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Brompheniramine; Guaifenesin; Hydrocodone: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Brompheniramine; Hydrocodone; Pseudoephedrine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Brompheniramine; Pseudoephedrine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Budesonide: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Budesonide; Formoterol: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Bumetanide: (Moderate) Salicylates may decrease the diuretic, natriuretic, and antihypertensive actions of diuretics, possibly through inhibition of renal prostaglandin synthesis. Patients receiving loop diuretics and salicylates should be monitored for changes in the effectiveness of their diuretic therapy.
    Buprenorphine: (Major) Concurrent use of opioids, such as buprenorphine, with other drugs that modulate serotonergic function, such as methylene blue, has resulted in serotonin syndrome in some cases. Serotonin syndrome is characterized by the rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. If combination treatment is required, patients should be carefully observed, particularly during treatment initiation and during dose adjustments of the serotonergic drug; discontinue buprenorphine if serotonin syndrome is suspected. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when buprenorphine is used concomitantly with an anticholinergic drug. The concomitant use of buprenorphine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Buprenorphine; Naloxone: (Major) Concurrent use of opioids, such as buprenorphine, with other drugs that modulate serotonergic function, such as methylene blue, has resulted in serotonin syndrome in some cases. Serotonin syndrome is characterized by the rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. If combination treatment is required, patients should be carefully observed, particularly during treatment initiation and during dose adjustments of the serotonergic drug; discontinue buprenorphine if serotonin syndrome is suspected. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when buprenorphine is used concomitantly with an anticholinergic drug. The concomitant use of buprenorphine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Bupropion: (Severe) Due to an increased risk of hypertensive reactions, treatment initiation with bupropion is contraindicated in patients currently receiving intravenous methylene blue. If urgent psychiatric treatment is required, interventions other than bupropion (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving bupropion and requiring urgent treatment with intravenous methylene blue, bupropion should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits of methylene blue outweigh the risks. The patient should be monitored for hypertensive reactions for two weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Bupropion may be re-initiated 24 hours after the last dose of methylene blue. It is not known if administration of methylene blue by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. (Moderate) Additive anticholinergic effects may be seen when hyoscyamine is used concomitantly with bupropion. Additive drowsiness may occur. Clinicians should note that antimuscarinic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation.
    Bupropion; Naltrexone: (Severe) Due to an increased risk of hypertensive reactions, treatment initiation with bupropion is contraindicated in patients currently receiving intravenous methylene blue. If urgent psychiatric treatment is required, interventions other than bupropion (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving bupropion and requiring urgent treatment with intravenous methylene blue, bupropion should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits of methylene blue outweigh the risks. The patient should be monitored for hypertensive reactions for two weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Bupropion may be re-initiated 24 hours after the last dose of methylene blue. It is not known if administration of methylene blue by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. (Moderate) Additive anticholinergic effects may be seen when hyoscyamine is used concomitantly with bupropion. Additive drowsiness may occur. Clinicians should note that antimuscarinic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation.
    Buspirone: (Moderate) Theoretically, concurrent use of methylene blue and buspirone may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and buspirone increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Butorphanol: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when butorphanol is used concomitantly with an anticholinergic drug. The concomitant use of butorphanol and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Cabergoline: (Moderate) Theoretically, concurrent use of methylene blue and cabergoline, an ergot derivative, may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and ergot alkaloids increase central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Caffeine: (Major) Sodium phosphates should be used with caution in patients using concomitant medications that lower the seizure threshold like psychostimulants.
    Caffeine; Ergotamine: (Moderate) Theoretically, concurrent use of methylene blue and ergot alkaloids may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and ergot alkaloids increase central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Calcium Carbonate: (Severe) Calcium carbonate increases urinary pH. Increased urinary pH can antagonize the actions of methenamine. Staggering the administration times will not prevent this interaction. (Moderate) Antacids may inhibit the oral absorption of antimuscarinics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction. (Minor) By increasing urinary pH, calcium carbonate can increase the urinary excretion of salicylates.
    Calcium Carbonate; Magnesium Hydroxide: (Severe) Calcium carbonate increases urinary pH. Increased urinary pH can antagonize the actions of methenamine. Staggering the administration times will not prevent this interaction. (Major) Aluminum hydroxide and magnesium hydroxide (as well as other antacids, i.e. aluminum hydroxide; magnesium carbonate, aluminum hydroxide; magaldrate; magnesium hydroxide, and aluminum hydroxide; magnesium trisilicate) may interact with urinary acidifiers by alkalinizing the urine. Frequent use of these high dose antacids should be avoided in patients receiving urinary acidifiers. (Major) The therapeutic action of methenamine requires an acidic urine. Antacids containing alkalinizing agents such as sodium bicarbonate can alkalinize the urine, thereby decreasing the effectiveness of methenamine by increasing the amount of non-ionized drug available for renal tubular reabsorption. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended. (Moderate) Antacids may inhibit the oral absorption of anticholinergics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction. (Moderate) Antacids may inhibit the oral absorption of antimuscarinics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction. (Minor) By increasing urinary pH, calcium carbonate can increase the urinary excretion of salicylates.
    Calcium Carbonate; Risedronate: (Severe) Calcium carbonate increases urinary pH. Increased urinary pH can antagonize the actions of methenamine. Staggering the administration times will not prevent this interaction. (Moderate) Antacids may inhibit the oral absorption of antimuscarinics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction. (Minor) By increasing urinary pH, calcium carbonate can increase the urinary excretion of salicylates.
    Calcium; Vitamin D: (Severe) Calcium carbonate increases urinary pH. Increased urinary pH can antagonize the actions of methenamine. Staggering the administration times will not prevent this interaction. (Moderate) Antacids may inhibit the oral absorption of antimuscarinics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction. (Minor) By increasing urinary pH, calcium carbonate can increase the urinary excretion of salicylates.
    Canagliflozin: (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Canagliflozin; Metformin: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control. (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Candesartan; Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Capreomycin: (Major) Since capreomycin is eliminated by the kidney, coadministration with other potentially nephrotoxic drugs, including salicylates, may increase serum concentrations of either drug. Theoretically, the chronic coadministration of these drugs may increase the risk of developing nephrotoxicity, even in patients who have normal renal function. Monitor patients for changes in renal function if these drugs are coadministered.
    Captopril: (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation.
    Captopril; Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Carbetapentane; Chlorpheniramine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including anticholinergics. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Carbetapentane; Chlorpheniramine; Phenylephrine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including anticholinergics. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Carbetapentane; Diphenhydramine; Phenylephrine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including anticholinergics. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Carbetapentane; Guaifenesin: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including anticholinergics.
    Carbetapentane; Guaifenesin; Phenylephrine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including anticholinergics.
    Carbetapentane; Phenylephrine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including anticholinergics.
    Carbetapentane; Phenylephrine; Pyrilamine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including anticholinergics. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Carbetapentane; Pseudoephedrine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including anticholinergics.
    Carbetapentane; Pyrilamine: (Moderate) Drowsiness has been reported during administration of carbetapentane. An enhanced CNS depressant effect may occur when carbetapentane is combined with other CNS depressants including anticholinergics. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Carbidopa; Levodopa: (Minor) Through its central antimuscarinic actions, hyoscyamine can potentiate the dopaminergic effects of levodopa. Clinicians should be ready to decrease doses of levodopa if hyoscyamine is added.
    Carbidopa; Levodopa; Entacapone: (Minor) Through its central antimuscarinic actions, hyoscyamine can potentiate the dopaminergic effects of levodopa. Clinicians should be ready to decrease doses of levodopa if hyoscyamine is added.
    Carbinoxamine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Carbinoxamine; Dextromethorphan; Pseudoephedrine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Carbinoxamine; Hydrocodone; Phenylephrine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Carbinoxamine; Hydrocodone; Pseudoephedrine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Carbinoxamine; Phenylephrine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Carbinoxamine; Pseudoephedrine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Cefixime: (Minor) In vitro, salicylates have displaced cefixime from its protein-binding sites, resulting in a 50% increase in free cefixime levels. The clinical significance of this effect is unclear at this time.
    Cefotetan: (Minor) Cefotetan has been associated with hypoprothrombinemia and may cause additive effects when given concurrently with salicylates.
    Celecoxib: (Major) Use celecoxib and salicylates in combination with caution. Analgesic doses of salicylates with celecoxib is not recommended due to additive gastrointestinal toxicity without additional analgesic benefit. Furthermore, cardioprotective doses of aspirin in combination with celecoxib are associated with an increased risk of gastrointestinal toxicity. In patients receiving low-dose aspirin with celecoxib over a 9-month period, GI bleeding, perforation, or obstruction was higher compared to patients taking celecoxib only (2.19% for combination vs. 0.78% for celecoxib only). Celecoxib does not exhibit antiplatelet effects and is not a substitute for aspirin when used for cardiovascular prophylaxis. However, there is no consistent evidence that concurrent use of aspirin with celecoxib mitigates the increased risk of serious cardiovascular thrombotic events associated with NSAID use.
    Cetirizine: (Moderate) Dry mouth and drowsiness were more common in patients receiving cetirizine/levocetirizine vs. placebo, and caution may be necessary during concomitant use of cetirizine/levocetirizine with the antimuscarinics.
    Cetirizine; Pseudoephedrine: (Moderate) Dry mouth and drowsiness were more common in patients receiving cetirizine/levocetirizine vs. placebo, and caution may be necessary during concomitant use of cetirizine/levocetirizine with the antimuscarinics.
    Chlophedianol; Dexchlorpheniramine; Pseudoephedrine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorcyclizine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorothiazide: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Chlorpheniramine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpheniramine; Codeine: (Severe) Codeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of codeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as codeine. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when codeine is used concomitantly with an anticholinergic drug. The concomitant use of codeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpheniramine; Dextromethorphan: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpheniramine; Dextromethorphan; Phenylephrine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Severe) Dihydrocodeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of dihydrocodeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as dihydrocodeine. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when dihydrocodeine is used concomitantly with an anticholinergic drug. The concomitant use of dihydrocodeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpheniramine; Dihydrocodeine; Pseudoephedrine: (Severe) Dihydrocodeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of dihydrocodeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as dihydrocodeine. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when dihydrocodeine is used concomitantly with an anticholinergic drug. The concomitant use of dihydrocodeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpheniramine; Guaifenesin; Hydrocodone; Pseudoephedrine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpheniramine; Hydrocodone: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpheniramine; Hydrocodone; Phenylephrine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpheniramine; Hydrocodone; Pseudoephedrine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpheniramine; Phenylephrine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpheniramine; Pseudoephedrine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Chlorpromazine: (Moderate) Additive anticholinergic effects may be seen when anticholinergics are used concomitantly with phenothiazines, including chlorpromazine. Clinicians should note that antimuscarinic effects may be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness or other additive CNS effects may also occur.
    Chlorthalidone: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Chlorthalidone; Clonidine: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Choline Salicylate; Magnesium Salicylate: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic.
    Cholinergic agonists: (Major) The muscarinic actions of drugs known as parasympathomimetics, including both direct cholinergic receptor agonists and cholinesterase inhibitors, can antagonize the antimuscarinic actions of anticholinergic drugs, and vice versa.
    Chondroitin; Glucosamine: (Moderate) The therapeutic action of methenamine requires an acidic urine. Ascorbic acid, vitamin C can produce unpredictable changes in urine pH and should be avoided as a urinary acidifier. In addition, orange juice also should be avoided because citric acid ultimately may raise urine pH. (Minor) Agents that acidify the urine should be avoided in patients receiving high-dose salicylates. Urinary pH changes can decrease salicylate excretion. If the urine is acidic prior to administration of an acidifying agent, the interaction should be minimal.
    Ciclesonide: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Cisapride: (Moderate) The use of drugs that decrease GI motility, such as hyoscyamine, may pharmacodynamically oppose the effects of cisapride.
    Citalopram: (Severe) According to the manufacturer of citalopram, treatment initiation with citalopram is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than citalopram (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving citalopram and requiring urgent treatment with IV methylene blue, citalopram should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 2 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Citalopram may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin; therefore, concurrent use of an MAO-A inhibitor with a serotonergic agent may result in a clinically significant interaction. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent, in patients receiving SSRIs, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. One case describes a patient receiving citalopram who experienced agitation, restlessness, pupil dilation with sluggish response to light, myoclonic movements of the lower limbs, and brisk reflexes following an infusion of methylene blue, while another patient receiving paroxetine developed tachycardia, agitation, dystonia and abnormal eye movements. During a retrospective study of 193 surgical patients who had received a methylene blue injection, it was found that all 12 of the patients who experienced postoperative neurological sequelae had been taking a serotonin reuptake inhibitor preoperatively. One of the 12 patients experienced cardiopulmonary arrest and died. Of the remaining 181 patients who did not experience neurological sequelae, 8.8% were taking a serotonin reuptake inhibitor. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma. (Moderate) The combined use of selective serotonin reuptake inhibitors (SSRIs) and aspirin, ASA or other salicylates which affect hemostasis may elevate the risk for an upper GI bleed. SSRIs may inhibit serotonin uptake by platelets, augmenting the antiplatelet effects of aspirin.
    Citric Acid; Potassium Citrate: (Major) The therapeutic action of methenamine requires an acidic urine. Alkalinizing agents, such as citrate salts, can alkalinize the urine, thereby decreasing the effectiveness of methenamine by increasing the amount of non-ionized drug available for renal tubular reabsorption. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended. (Moderate) Urinary alkalinizing agents, like potassium citrate, increase the excretion of salicylates by increasing renal clearance.
    Citric Acid; Potassium Citrate; Sodium Citrate: (Major) The therapeutic action of methenamine requires an acidic urine. Alkalinizing agents, such as citrate salts, can alkalinize the urine, thereby decreasing the effectiveness of methenamine by increasing the amount of non-ionized drug available for renal tubular reabsorption. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended. (Moderate) Urinary alkalinizing agents, like potassium citrate, increase the excretion of salicylates by increasing renal clearance.
    Clemastine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Clomipramine: (Severe) According to the manufacturer of clomipramine, treatment initiation with clomipramine is contraindicated in patients currently receiving intravenous methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than clomipramine (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving clomipramine and requiring urgent treatment with intravenous methylene blue, clomipramine should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits of methylene blue outweigh the risks. The patient should be monitored for serotonin syndrome for two weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Clomipramine may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin; therefore, concurrent use of an MAO-A inhibitor with a serotonergic agent may result in a clinically significant interaction. Clomipramine, a tricyclic antidepressant, is the most selective and potent inhibitor of serotonin within its class. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. One case report describes a patient receiving clomipramine who experienced jerky movements in all four limbs, as well as confusion and agitation after intravenous administration of methylene blue, with a return to her pre-operative state by day 4. Although the authors attribute this reaction to methylene blue toxicity, they did not exclude the possibility of a drug interaction based upon previous reports of an interaction between injectable methylene blue and selective serotonin reuptake inhibitors (SSRIs). Published interaction reports between intravenousely administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma.
    Clozapine: (Moderate) Additive anticholinergic effects may be seen when hyoscyamine is used with other drugs with moderate to significant anticholinergic effects including clozapine.
    Cobicistat; Elvitegravir; Emtricitabine; Tenofovir Disoproxil Fumarate: (Major) Renal impairment, which may include hypophosphatemia, has been reported with the use of tenofovir disoproxil fumarate with a majority of the cases occurring in patients who have underlying systemic or renal disease or who are concurrently taking nephrotoxic agents. Tenofovir should be avoided with concurrent or recent use of a nephrotoxic agent; patients receiving concomitant nephrotoxic agents, like salicylates should be carefully monitored for changes in serum creatinine and phosphorus.
    Codeine: (Severe) Codeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of codeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as codeine. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when codeine is used concomitantly with an anticholinergic drug. The concomitant use of codeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Codeine; Guaifenesin: (Severe) Codeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of codeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as codeine. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when codeine is used concomitantly with an anticholinergic drug. The concomitant use of codeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Codeine; Phenylephrine; Promethazine: (Severe) Codeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of codeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as codeine. (Moderate) Additive anticholinergic effects may be seen when anticholinergics are used concomitantly with phenothiazines, including promethazine. Clinicians should note that antimuscarinic effects may be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness or other additive CNS effects may also occur. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when codeine is used concomitantly with an anticholinergic drug. The concomitant use of codeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Codeine; Promethazine: (Severe) Codeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of codeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as codeine. (Moderate) Additive anticholinergic effects may be seen when anticholinergics are used concomitantly with phenothiazines, including promethazine. Clinicians should note that antimuscarinic effects may be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness or other additive CNS effects may also occur. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when codeine is used concomitantly with an anticholinergic drug. The concomitant use of codeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Colchicine: (Moderate) Colchicine is an alkaloid that is inhibited by acidifying agents. The colchicine dose may need adjustment
    Colistimethate, Colistin, Polymyxin E: (Major) Theoretically, the chronic coadministration of these drugs may increase the risk of developing nephrotoxicity, even in patients who have normal renal function. Monitor patients for changes in renal function if these drugs are coadministered. Since colistimethate sodium is eliminated by the kidney, coadministration with other potentially nephrotoxic drugs, including salicylates, may increase serum concentrations of either drug.
    Collagenase: (Moderate) The therapeutic action of methenamine requires an acidic urine. Ascorbic acid, vitamin C can produce unpredictable changes in urine pH and should be avoided as a urinary acidifier. In addition, orange juice also should be avoided because citric acid ultimately may raise urine pH. (Minor) Agents that acidify the urine should be avoided in patients receiving high-dose salicylates. Urinary pH changes can decrease salicylate excretion. If the urine is acidic prior to administration of an acidifying agent, the interaction should be minimal.
    Corticosteroids: (Moderate) Salicylates or NSAIDs should be used cautiously in patients receiving corticosteroids. While there is controversy regarding the ulcerogenic potential of corticosteroids alone, concomitant administration of corticosteroids with aspirin may increase the GI toxicity of aspirin and other non-acetylated salicylates. Withdrawal of corticosteroids can result in increased plasma concentrations of salicylate and possible toxicity. Concomitant use of corticosteroids may increase the risk of adverse GI events due to NSAIDs. Although some patients may need to be given corticosteroids and NSAIDs concomitantly, which can be done successfully for short periods of time without sequelae, prolonged coadministration should be avoided. (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Corticotropin, ACTH: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Cortisone: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Cranberry, Vaccinium macrocarpon Ait.: (Moderate) The therapeutic action of methenamine requires an acidic urine. Ascorbic acid, vitamin C can produce unpredictable changes in urine pH and should be avoided as a urinary acidifier. In addition, orange juice also should be avoided because citric acid ultimately may raise urine pH. (Minor) Agents that acidify the urine should be avoided in patients receiving high-dose salicylates. Urinary pH changes can decrease salicylate excretion. If the urine is acidic prior to administration of an acidifying agent, the interaction should be minimal.
    Crofelemer: (Moderate) Pharmacodynamic interactions between crofelemer and antimuscarinics are theoretically possible. Crofelemer does not affect GI motility mechanisms, but does have antidiarrheal effects. Patients taking medications that decrease GI motility, such as antimuscarinics, may be at greater risk for serious complications from crofelemer, such as constipation with chronic use. Use caution and monitor GI symptoms during coadministration.
    Cyclizine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Cyclobenzaprine: (Moderate) Depending on the specific agent, additive anticholinergic effects may be seen when drugs with antimuscarinic properties like cyclobenzaprine are used concomitantly with other anticholinergics. Clinicians should note that additive antimuscarinic effects may be seen not only on GI smooth muscle, but also on bladder function, the CNS, the eye, and temperature regulation. Additive drowsiness may also occur, depending on the interacting agent.
    Cyclosporine: (Minor) Due to the inhibition of renal prostaglandins by salicylates, concurrent use of salicylates and other nephrotoxic agents like cyclosporine may lead to additive nephrotoxicity.
    Cyproheptadine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Dalteparin: (Moderate) An additive risk of bleeding may be seen in patients receiving a low molecular weight heparin in combination with other agents known to increase the risk of bleeding such as salicylates. Monitor clinical and laboratory response closely during concurrent use.
    Dapagliflozin: (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Dapagliflozin; Metformin: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control. (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Dapagliflozin; Saxagliptin: (Moderate) Salicylates can indirectly increase insulin secretion, decreasing blood glucose concentrations. In large doses, salicylates may cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving saxagliptin. (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Deferasirox: (Moderate) Because gastric ulceration and GI bleeding have been reported in patients taking deferasirox, use caution when coadministering with other drugs known to increase the risk of peptic ulcers or gastric hemorrhage including salicylates.
    Deflazacort: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Desipramine: (Severe) According to the manufacturer, treatment initiation with desipramine is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than desipramine (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving desipramine and requiring urgent treatment with IV methylene blue, desipramine should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 2 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Desipramine may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent, in patients receiving serotonergic agents. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma.
    Desvenlafaxine: (Severe) Concurrent use of methylene blue and serotonin norepinephrine reuptake inhibitors (SNRIs) (e.g., venlafaxine, duloxetine, desvenlafaxine, milnacipran) should generally be avoided due to the potential for serotonin syndrome. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin; therefore, concurrent use of an MAO-A inhibitor with serotonergic agents such as SNRIs may result in a clinically significant interaction. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, SNRIs, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. One case report suggests that serotonin toxicity may have occurred post-operatively following administration of standard infusions of methylene blue in a patient receiving duloxetine. The patient experienced disorientation, a mildly elevated temperature, tachycardia, elevated blood pressure, mild agitation, and nystagmus. In a separate case, a patient who had been receiving venlafaxine developed expressive aphasia, confusion, and disinhibition following a methylene blue infusion. The authors concluded that methylene blue toxicity had occurred; however, they did not exclude the possibility of a drug interaction based upon previous reports of an interaction between injectable methylene blue and selective serotonin reuptake inhibitors (SSRIs). Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma. If emergent treatment with methylene blue is required in a patient receiving an SNRI, the SNRI must be stopped immediately and the patient should be monitored for symptoms of CNS toxicity for two weeks or until 24 hours after the last dose of methylene blue, whichever comes first. During non-emergent use of methylene blue, the SNRI should be stopped at least 2 weeks prior to methylene blue treatment, but also taking into consideration the half-life of the SNRI being discontinued.
    Dexamethasone: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Dexchlorpheniramine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Dexchlorpheniramine; Dextromethorphan; Pseudoephedrine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Dexmethylphenidate: (Moderate) Theoretically, concurrent use of methylene blue and dexmethylphenidate may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dexmethylphenidate increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by the rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. If serotonin syndrome occurs, all serotonergic agents should be discontinued and appropriate medical management should be implemented.
    Dextroamphetamine: (Severe) Amphetamines should not be administered during or within 14 days after the use of methylene blue. Methylene blue is a potent, reversible monoamine oxidase inhibitor (MAOI) which can prolong and intensify the cardiac stimulation and vasopressor effects of amphetamines, potentially resulting in hypertensive crisis. Methylene blue also has the potential to interact with serotonergic agents, such as amphetamines, which may increase the risk for serotonin syndrome. Serotonin syndrome is characterized by mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea), and in rare instances, death. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents, such as amphetamines, with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma.
    Dextromethorphan: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Dextromethorphan; Diphenhydramine; Phenylephrine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Dextromethorphan; Guaifenesin: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Dextromethorphan; Guaifenesin; Phenylephrine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Dextromethorphan; Guaifenesin; Potassium Guaiacolsulfonate: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Dextromethorphan; Guaifenesin; Pseudoephedrine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Dextromethorphan; Promethazine: (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. (Moderate) Additive anticholinergic effects may be seen when anticholinergics are used concomitantly with phenothiazines, including promethazine. Clinicians should note that antimuscarinic effects may be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness or other additive CNS effects may also occur.
    Dextromethorphan; Quinidine: (Major) Hyoscyamine may increase the absorption of quinidine by decreasing GI motility and thereby enhancing absorption with possible toxicity. Increased monitoring is advised in patients receiving a combination of these drugs. (Major) Theoretically, concurrent use of methylene blue and dextromethorphan may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and dextromethorphan increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Diazoxide: (Moderate) Use sodium phosphates cautiously with diazoxide, as concurrent use can cause hypernatremia.
    Dichlorphenamide: (Moderate) Use dichlorphenamide and sodium phosphate monobasic monohydrate; sodium phosphate dibasic anhydrous together with caution. Dichlorphenamide increases potassium excretion and can cause hypokalemia and should be used cautiously with other drugs that may cause hypokalemia including laxatives. Measure potassium concentrations at baseline and periodically during dichlorphenamide treatment. If hypokalemia occurs or persists, consider reducing the dichlorphenamide dose or discontinuing dichlorphenamide therapy.
    Diclofenac: (Major) Increased adverse gastrointestinal effects, including gastric ulceration or blood loss, are possible if diclofenac is used with salicylates. The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function.
    Diclofenac; Misoprostol: (Major) Increased adverse gastrointestinal effects, including gastric ulceration or blood loss, are possible if diclofenac is used with salicylates. The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function.
    Diflunisal: (Major) The concurrent use of diflunisal and salicylates is not recommended due to the increased risk of gastrointestinal toxicity with little or no increase in anti-inflammatory efficacy.
    Digoxin: (Moderate) Anticholinergics, because of their ability to cause tachycardia, can antagonize the beneficial actions of digoxin in atrial fibrillation/flutter. Routine therapeutic monitoring should be continued when an antimuscarinic agent is prescribed with digoxin until the effects of combined use are known.
    Dihydrocodeine; Guaifenesin; Pseudoephedrine: (Severe) Dihydrocodeine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of dihydrocodeine with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as dihydrocodeine. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when dihydrocodeine is used concomitantly with an anticholinergic drug. The concomitant use of dihydrocodeine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Dihydroergotamine: (Moderate) Theoretically, concurrent use of methylene blue and ergot alkaloids may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and ergot alkaloids increase central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Dimenhydrinate: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Diphenhydramine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Diphenhydramine; Hydrocodone; Phenylephrine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Diphenhydramine; Ibuprofen: (Major) The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function. The use of salicylates together with NSAIDs can also lead to additive GI toxicity. The FDA issued an advisory that 400 mg of ibuprofen can interfere with the antiplatelet effects of low dose aspirin (81 mg per day). Routine use of ibuprofen is likely to have the most significant effect. The FDA recommends administering ibuprofen 8 hours before or 30 minutes after aspirin if concurrent therapy is needed. Interactions have been noted between ibuprofen and aspirin, ASA. Concurrent use of chronic ibuprofen therapy (800 mg three times daily) seems to antagonize the inhibition of platelet cyclooxygenase (COX)-1 activity and impairment of platelet aggregation by low-dose aspirin (81 mg once daily) per an ex vivo analysis. In this study, diclofenac or rofecoxib therapy, agents with less activity at COX-1 than ibuprofen, did not affect inhibition of platelet aggregation by aspirin. An in vitro study has shown that the antagonism of aspirin platelet inhibition probably involves competition at platelet-derived COX-1 and is related to the NSAIDs' ability to inhibit COX-1 mediated thromboxane B2 production in platelets. Clinically, the interaction may be more dramatic with regular as compared with intermittent ibuprofen usage. Quantification of the risk was determined by the analysis of retrospective data, which may be inaccurate and incomplete. However, a trend towards a greater risk of a second myocardial infarction in the year after the initial event among adults taking daily aspirin was associated with a greater length of ibuprofen exposure. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Diphenhydramine; Naproxen: (Major) Aspirin, ASA displaces naproxen from binding to albumin and increases naproxen excretion. Due to an increased free fraction of naproxen, increased adverse gastrointestinal effects are possible if naproxen is used with aspirin. In addition, further benefit with use of the two drugs as compared with aspirin monotherapy is not apparent, and antagonism of the irreversible platelet effect of aspirin occurs with concurrent use. The interaction appears to be due to competition at the enzyme active site. Patients who take low-dose aspirin for cardiovascular health may have the beneficial effects of aspirin on platelet function counteracted by naproxen. Concomitant aspirin and naproxen use is not recommended. The use of Naproxen with other salicylates can also lead to additive GI toxicity. (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Diphenhydramine; Phenylephrine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Disopyramide: (Moderate) In addition to its electrophysiologic effects, disopyramide exhibits clinically significant anticholinergic properties. These can be additive with other anticholinergics. Clinicians should be aware that urinary retention, particularly in males, and aggravation of glaucoma are realistic possibilities of using disopyramide with other anticholinergic agents.
    Dolasetron: (Major) Because of the potential risk and severity of serotonin syndrome, use caution when administering dolasetron with other drugs that have serotonergic properties such as methylene blue. If serotonin syndrome is suspected, discontinue dolasetron and concurrent serotonergic agents and initiate appropriate medical treatment. Serotonin syndrome is characterized by rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death.
    Donepezil: (Moderate) The therapeutic benefits of donepezil, a cholinesterase inhibitor, may be diminished during chronic co-administration with antimuscarinics or medications with potent anticholinergic activity. When concurrent use is not avoidable, the patient should be monitored for cognitive decline and anticholinergic side effects. Clinicians should generally avoid multiple medications with anticholinergic activity in the patient with dementia. Some of the common selective antimuscarinic drugs for bladder problems, (such as oxybutynin, darifenacin, trospium, fesoterodine, tolerodine, or solifenacin), do not routinely cause problems with medications used for dementia, but may cause anticholinergic side effects in some patients. Atropine may be used to offset bradycardia in cholinesterase inhibitor overdose.
    Donepezil; Memantine: (Moderate) The adverse effects of anticholinergics, such as dry mouth, urinary hesitancy or blurred vision may be enhanced with use of memantine; dosage adjustments of the anticholinergic drug may be required when memantine is coadministered. In addition, preliminary evidence indicates that chronic anticholinergic use in patients with Alzheimer's Disease may possibly have an adverse effect on cognitive function. Therefore, the effectiveness of drugs used in the treatment of Alzheimer's such as memantine, may be adversely affected by chronic antimuscarinic therapy. (Moderate) The therapeutic benefits of donepezil, a cholinesterase inhibitor, may be diminished during chronic co-administration with antimuscarinics or medications with potent anticholinergic activity. When concurrent use is not avoidable, the patient should be monitored for cognitive decline and anticholinergic side effects. Clinicians should generally avoid multiple medications with anticholinergic activity in the patient with dementia. Some of the common selective antimuscarinic drugs for bladder problems, (such as oxybutynin, darifenacin, trospium, fesoterodine, tolerodine, or solifenacin), do not routinely cause problems with medications used for dementia, but may cause anticholinergic side effects in some patients. Atropine may be used to offset bradycardia in cholinesterase inhibitor overdose.
    Doxepin: (Severe) According to the manufacturer, treatment initiation with doxepin is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than doxepin (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving doxepin and requiring urgent treatment with IV methylene blue, doxepin should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 2 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Doxepin may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent, in patients receiving serotonergic agents. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma.
    Doxylamine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Doxylamine; Pyridoxine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Dronabinol, THC: (Moderate) Use caution if coadministration of dronabinol with anticholinergics is necessary. Concurrent use of dronabinol, THC with anticholinergics may result in additive drowsiness, hypertension, tachycardia, and possibly cardiotoxicity.
    Drotrecogin Alfa: (Major) Treatment with drotrecogin alfa should be carefully considered in patients who are receiving or have received salicylates within 7 days. These patients are at increased risk of bleeding during drotrecogin alfa therapy. Caution should be used when drotrecogin alfa is used with any other drugs that affect hemostasis.
    Duloxetine: (Severe) Concurrent use of methylene blue and serotonin norepinephrine reuptake inhibitors (SNRIs) (e.g., venlafaxine, duloxetine, desvenlafaxine, milnacipran) should generally be avoided due to the potential for serotonin syndrome. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin; therefore, concurrent use of an MAO-A inhibitor with serotonergic agents such as SNRIs may result in a clinically significant interaction. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, SNRIs, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. One case report suggests that serotonin toxicity may have occurred post-operatively following administration of standard infusions of methylene blue in a patient receiving duloxetine. The patient experienced disorientation, a mildly elevated temperature, tachycardia, elevated blood pressure, mild agitation, and nystagmus. In a separate case, a patient who had been receiving venlafaxine developed expressive aphasia, confusion, and disinhibition following a methylene blue infusion. The authors concluded that methylene blue toxicity had occurred; however, they did not exclude the possibility of a drug interaction based upon previous reports of an interaction between injectable methylene blue and selective serotonin reuptake inhibitors (SSRIs). Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma. If emergent treatment with methylene blue is required in a patient receiving an SNRI, the SNRI must be stopped immediately and the patient should be monitored for symptoms of CNS toxicity for two weeks or until 24 hours after the last dose of methylene blue, whichever comes first. During non-emergent use of methylene blue, the SNRI should be stopped at least 2 weeks prior to methylene blue treatment, but also taking into consideration the half-life of the SNRI being discontinued.
    Edoxaban: (Major) Large doses of salicylates (>= 3-4 g/day) can cause hypoprothrombinemia, an additional risk factor for bleeding. Patients taking large doses of salicylates and edoxaban should be monitored closely for bleeding.
    Edrophonium: (Major) The muscarinic actions of edrophonium chloride can antagonize the antimuscarinic actions of hyoscyamine.
    Efavirenz; Emtricitabine; Tenofovir: (Major) Renal impairment, which may include hypophosphatemia, has been reported with the use of tenofovir disoproxil fumarate with a majority of the cases occurring in patients who have underlying systemic or renal disease or who are concurrently taking nephrotoxic agents. Tenofovir should be avoided with concurrent or recent use of a nephrotoxic agent; patients receiving concomitant nephrotoxic agents, like salicylates should be carefully monitored for changes in serum creatinine and phosphorus.
    Eluxadoline: (Major) Avoid use of eluxadoline with medications that may cause constipation, such as anticholinergics. Discontinue use of eluxadoline in patients who develop severe constipation lasting more than 4 days.
    Empagliflozin: (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Empagliflozin; Linagliptin: (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents, such as linagliptin. (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Empagliflozin; Metformin: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control. (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Emtricitabine; Rilpivirine; Tenofovir disoproxil fumarate: (Major) Renal impairment, which may include hypophosphatemia, has been reported with the use of tenofovir disoproxil fumarate with a majority of the cases occurring in patients who have underlying systemic or renal disease or who are concurrently taking nephrotoxic agents. Tenofovir should be avoided with concurrent or recent use of a nephrotoxic agent; patients receiving concomitant nephrotoxic agents, like salicylates should be carefully monitored for changes in serum creatinine and phosphorus.
    Emtricitabine; Tenofovir disoproxil fumarate: (Major) Renal impairment, which may include hypophosphatemia, has been reported with the use of tenofovir disoproxil fumarate with a majority of the cases occurring in patients who have underlying systemic or renal disease or who are concurrently taking nephrotoxic agents. Tenofovir should be avoided with concurrent or recent use of a nephrotoxic agent; patients receiving concomitant nephrotoxic agents, like salicylates should be carefully monitored for changes in serum creatinine and phosphorus.
    Enalapril, Enalaprilat: (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation.
    Enalapril; Felodipine: (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation.
    Enalapril; Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Enoxaparin: (Moderate) An additive risk of bleeding may be seen in patients receiving a low molecular weight heparin in combination with other agents known to increase the risk of bleeding such as salicylates. Monitor clinical and laboratory response closely during concurrent use.
    Eprosartan; Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Ergoloid Mesylates: (Moderate) Theoretically, concurrent use of methylene blue and ergot alkaloids may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and ergot alkaloids increase central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Ergonovine: (Moderate) Theoretically, concurrent use of methylene blue and ergot alkaloids may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and ergot alkaloids increase central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Ergot alkaloids: (Moderate) Theoretically, concurrent use of methylene blue and ergot alkaloids may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and ergot alkaloids increase central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Ergotamine: (Moderate) Theoretically, concurrent use of methylene blue and ergot alkaloids may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and ergot alkaloids increase central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Erythromycin: (Moderate) Anticholinergics can antagonize the stimulatory effects of erythromycin on the GI tract (when erythromycin is used therapeutically for improving GI motility). Avoid chronic administration of antimuscarinics along with prokinetic agents under most circumstances. In addition, erythromycin is a CYP3A4 inhibitor and can reduce the metabolism of drugs metabolized by CYP3A4, including some anticholinergics.
    Erythromycin; Sulfisoxazole: (Major) Sulfonamides can crystallize in an acidic urine. Because methenamine salts produce an acidic urine, these agents should not be used concomitantly. (Moderate) Anticholinergics can antagonize the stimulatory effects of erythromycin on the GI tract (when erythromycin is used therapeutically for improving GI motility). Avoid chronic administration of antimuscarinics along with prokinetic agents under most circumstances. In addition, erythromycin is a CYP3A4 inhibitor and can reduce the metabolism of drugs metabolized by CYP3A4, including some anticholinergics.
    Escitalopram: (Severe) According to the manufacturer of escitalopram, treatment initiation with escitalopram is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than escitalopram (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving escitalopram and requiring urgent treatment with IV methylene blue, escitalopram should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 2 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Escitalopram may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin; therefore, concurrent use of an MAO-A inhibitor with a serotonergic agent may result in a clinically significant interaction. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent, in patients receiving SSRIs, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. One case describes a patient receiving citalopram who experienced agitation, restlessness, pupil dilation with sluggish response to light, myoclonic movements of the lower limbs, and brisk reflexes following an infusion of methylene blue, while another patient receiving paroxetine developed tachycardia, agitation, dystonia and abnormal eye movements. During a retrospective study of 193 surgical patients who had received a methylene blue injection, it was found that all 12 of the patients who experienced postoperative neurological sequelae had been taking a serotonin reuptake inhibitor preoperatively. One of the 12 patients experienced cardiopulmonary arrest and died. Of the remaining 181 patients who did not experience neurological sequelae, 8.8% were taking a serotonin reuptake inhibitor. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma. (Moderate) The combined use of selective serotonin reuptake inhibitors (SSRIs) and aspirin, ASA or other salicylates which affect hemostasis may elevate the risk for an upper GI bleed. SSRIs may inhibit serotonin uptake by platelets, augmenting the antiplatelet effects of aspirin.
    Esomeprazole; Naproxen: (Major) Aspirin, ASA displaces naproxen from binding to albumin and increases naproxen excretion. Due to an increased free fraction of naproxen, increased adverse gastrointestinal effects are possible if naproxen is used with aspirin. In addition, further benefit with use of the two drugs as compared with aspirin monotherapy is not apparent, and antagonism of the irreversible platelet effect of aspirin occurs with concurrent use. The interaction appears to be due to competition at the enzyme active site. Patients who take low-dose aspirin for cardiovascular health may have the beneficial effects of aspirin on platelet function counteracted by naproxen. Concomitant aspirin and naproxen use is not recommended. The use of Naproxen with other salicylates can also lead to additive GI toxicity.
    Ethacrynic Acid: (Moderate) Salicylates may decrease the diuretic, natriuretic, and antihypertensive actions of diuretics, possibly through inhibition of renal prostaglandin synthesis. Patients receiving loop diuretics and salicylates should be monitored for changes in the effectiveness of their diuretic therapy.
    Ethanol: (Major) Concomitant ingestion of ethanol with salicylates, especially aspirin, ASA, increases the risk of developing gastric irritation and GI mucosal bleeding. Ethanol and salicylates are mucosal irritants and aspirin decreases platelet aggregation. Routine ingestion of ethanol and aspirin can cause significant GI bleeding, which may or may not be overt. Even occasional concomitant use of salicylates and ethanol should be avoided. Chronic alcoholism is often associated with hypoprothrombinemia and this condition increases the risk of salicylate-induced bleeding. Patients should be warned regarding the potential for increased risk of GI bleeding if alcohol-containing beverages are taken concurrently with salicylates (Major) Sodium phosphate monobasic monohydrate; sodium phosphate dibasic anhydrous has been associated with seizure activity in patients with or without a prior history of seizures. Abrupt withdrawal from ethanol may increase the risk of seizures. Close monitoring is advised in patients receiving sodium phosphate monobasic monohydrate; sodium phosphate dibasic anhydrous who are withdrawing from ethanol.
    Ethotoin: (Minor) Large doses of salicylates can displace hydantoins from plasma protein-binding sites. Although increased serum concentrations of unbound phenytoin may lead to phenytoin toxicity, the liver may also more rapidly clear unbound drug.
    Etodolac: (Major) The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function. The use of salicylates together with NSAIDs can also lead to additive GI toxicity.
    Ezogabine: (Moderate) Caution is advisable during concurrent use of ezogabine and medications that may affect voiding such as anticholinergic agents. Ezogabine has caused urinary retention requiring catheterization in some cases. The anticholinergic effects of antimuscariinic and anticholinergic medications on the urinary tract may be additive. Additive sedation or other CNS effects may also occur.
    Famotidine; Ibuprofen: (Major) The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function. The use of salicylates together with NSAIDs can also lead to additive GI toxicity. The FDA issued an advisory that 400 mg of ibuprofen can interfere with the antiplatelet effects of low dose aspirin (81 mg per day). Routine use of ibuprofen is likely to have the most significant effect. The FDA recommends administering ibuprofen 8 hours before or 30 minutes after aspirin if concurrent therapy is needed. Interactions have been noted between ibuprofen and aspirin, ASA. Concurrent use of chronic ibuprofen therapy (800 mg three times daily) seems to antagonize the inhibition of platelet cyclooxygenase (COX)-1 activity and impairment of platelet aggregation by low-dose aspirin (81 mg once daily) per an ex vivo analysis. In this study, diclofenac or rofecoxib therapy, agents with less activity at COX-1 than ibuprofen, did not affect inhibition of platelet aggregation by aspirin. An in vitro study has shown that the antagonism of aspirin platelet inhibition probably involves competition at platelet-derived COX-1 and is related to the NSAIDs' ability to inhibit COX-1 mediated thromboxane B2 production in platelets. Clinically, the interaction may be more dramatic with regular as compared with intermittent ibuprofen usage. Quantification of the risk was determined by the analysis of retrospective data, which may be inaccurate and incomplete. However, a trend towards a greater risk of a second myocardial infarction in the year after the initial event among adults taking daily aspirin was associated with a greater length of ibuprofen exposure.
    Fenoprofen: (Major) The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function. The use of salicylates together with NSAIDs can also lead to additive GI toxicity.
    Fentanyl: (Major) The use of fentanyl is not recommended in patients who have received a monoamine oxidase inhibitor (MAOI) within 14 days. Methylene blue is a reversible inhibitor of MAO. Concomitant use of fentanyl with other serotonergic drugs such as MAOIs may result in serious adverse effects including serotonin syndrome. MAOIs may cause additive CNS depression, respiratory depression, drowsiness, dizziness, or hypotension when used with opiate agonists such as fentanyl. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when fentanyl is used concomitantly with an anticholinergic drug. The concomitant use of fentanyl and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Fludrocortisone: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Flunisolide: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Fluoxetine: (Severe) According to the manufacturer of fluoxetine, treatment initiation with fluoxetine is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than fluoxetine (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving fluoxetine and requiring urgent treatment with IV methylene blue, fluoxetine should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 5 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Fluoxetine may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin; therefore, concurrent use of an MAO-A inhibitor with a serotonergic agent may result in a clinically significant interaction. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent, in patients receiving SSRIs, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. One case describes a patient receiving citalopram who experienced agitation, restlessness, pupil dilation with sluggish response to light, myoclonic movements of the lower limbs, and brisk reflexes following an infusion of methylene blue, while another patient receiving paroxetine developed tachycardia, agitation, dystonia and abnormal eye movements. During a retrospective study of 193 surgical patients who had received a methylene blue injection, it was found that all 12 of the patients who experienced postoperative neurological sequelae had been taking a serotonin reuptake inhibitor preoperatively. One of the 12 patients experienced cardiopulmonary arrest and died. Of the remaining 181 patients who did not experience neurological sequelae, 8.8% were taking a serotonin reuptake inhibitor. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma. (Moderate) The combined use of selective serotonin reuptake inhibitors (SSRIs) and aspirin, ASA or other salicylates which affect hemostasis may elevate the risk for an upper GI bleed. SSRIs may inhibit serotonin uptake by platelets, augmenting the antiplatelet effects of aspirin.
    Fluoxetine; Olanzapine: (Severe) According to the manufacturer of fluoxetine, treatment initiation with fluoxetine is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than fluoxetine (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving fluoxetine and requiring urgent treatment with IV methylene blue, fluoxetine should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 5 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Fluoxetine may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin; therefore, concurrent use of an MAO-A inhibitor with a serotonergic agent may result in a clinically significant interaction. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent, in patients receiving SSRIs, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. One case describes a patient receiving citalopram who experienced agitation, restlessness, pupil dilation with sluggish response to light, myoclonic movements of the lower limbs, and brisk reflexes following an infusion of methylene blue, while another patient receiving paroxetine developed tachycardia, agitation, dystonia and abnormal eye movements. During a retrospective study of 193 surgical patients who had received a methylene blue injection, it was found that all 12 of the patients who experienced postoperative neurological sequelae had been taking a serotonin reuptake inhibitor preoperatively. One of the 12 patients experienced cardiopulmonary arrest and died. Of the remaining 181 patients who did not experience neurological sequelae, 8.8% were taking a serotonin reuptake inhibitor. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma. (Moderate) Olanzapine exhibits anticholinergic effects that may be enhanced when combined with other with anticholinergic activity including the hyoscyamine. Clinicians should note that additive antimuscarinic effects may be seen not only on GI smooth muscle, but also on bladder function, the CNS, the eye, and temperature regulation. Additive drowsiness may also occur. (Moderate) The combined use of selective serotonin reuptake inhibitors (SSRIs) and aspirin, ASA or other salicylates which affect hemostasis may elevate the risk for an upper GI bleed. SSRIs may inhibit serotonin uptake by platelets, augmenting the antiplatelet effects of aspirin.
    Fluphenazine: (Moderate) Additive anticholinergic effects may be seen when anticholinergics are used concomitantly with phenothiazines, including fluphenazine. Clinicians should note that antimuscarinic effects may be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness or other additive CNS effects may also occur.
    Flurbiprofen: (Major) The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function. The use of salicylates together with NSAIDs can also lead to additive GI toxicity.
    Fluticasone: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Fluticasone; Salmeterol: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Fluticasone; Umeclidinium; Vilanterol: (Moderate) There is the potential for umeclidinium to have additive anticholinergic effects when administered with other anticholinergics or antimuscarinics. Per the manufaturer, avoid concomitant administration of umeclidinium with other anticholinergic medications when possible. (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Fluticasone; Vilanterol: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Fluvoxamine: (Severe) According to the manufacturer of fluvoxamine, treatment initiation with fluvoxamine is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than fluvoxamine (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving fluvoxamine and requiring urgent treatment with IV methylene blue, fluvoxamine should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 2 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Fluvoxamine may be re-initiated 24 hours after the last dose of methylene blue. MAO-A is responsible for the metabolism of serotonin; therefore, concurrent use of an MAO-A inhibitor with a serotonergic agent may result in a clinically significant interaction. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving SSRIs, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. One case describes a patient receiving citalopram who experienced agitation, restlessness, pupil dilation with sluggish response to light, myoclonic movements of the lower limbs, and brisk reflexes following an infusion of methylene blue, while another patient receiving paroxetine developed tachycardia, agitation, dystonia and abnormal eye movements. During a retrospective study of 193 surgical patients who had received a methylene blue injection, it was found that all 12 of the patients who experienced postoperative neurological sequelae had been taking a serotonin reuptake inhibitor preoperatively. One of the 12 patients experienced cardiopulmonary arrest and died. Of the remaining 181 patients who did not experience neurological sequelae, 8.8% were taking a serotonin reuptake inhibitor. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma. (Moderate) The combined use of selective serotonin reuptake inhibitors (SSRIs) and aspirin, ASA or other salicylates which affect hemostasis may elevate the risk for an upper GI bleed. SSRIs may inhibit serotonin uptake by platelets, augmenting the antiplatelet effects of aspirin.
    Fondaparinux: (Moderate) An additive risk of bleeding may be seen in patients receiving platelet inhibitors (e.g. aspirin, ASA) in combination with fondaparinux. Data on the concomitant use of fondaparinux with aspirin are lacking; however, large doses of salicylates (>= 3-4 g/day) can cause hypoprothrombinemia, an additional risk factor for bleeding.
    Food: (Moderate) Methenamine should theoretically not be administered concurrently with food or beverages that may alter urinary pH, such as milk products and most fruits. These agents may cause the urine to become alkaline and reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. Orange juice is not a reliable urinary acidifier and should not be used to ensure urine acidification; citric acid may actually raise urine pH if taken in large amounts.
    Formoterol; Mometasone: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Foscarnet: (Minor) Due to the inhibition of renal prostaglandins by salicylates, concurrent use of salicylates and other nephrotoxic agents, such as foscarnet, may lead to additive nephrotoxicity.
    Fosinopril: (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation.
    Fosinopril; Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Fosphenytoin: (Minor) Large doses of salicylates can displace phenytoin from plasma protein-binding sites. Although increased serum concentrations of unbound phenytoin may lead to phenytoin toxicity, the liver may also more rapidly clear unbound drug. Fosphenytoin is converted to phenytoin in vivo, so this interaction may also occur with fosphenytoin.
    Furosemide: (Moderate) Salicylates may decrease the diuretic, natriuretic, and antihypertensive actions of diuretics, possibly through inhibition of renal prostaglandin synthesis. Patients receiving loop diuretics and salicylates should be monitored for changes in the effectiveness of their diuretic therapy.
    Galantamine: (Moderate) The therapeutic benefits of galantamine, a cholinesterase inhibitor, may be diminished during chronic co-administration with antimuscarinics or medications with potent anticholinergic activity. When concurrent use is not avoidable, the patient should be monitored for cognitive decline and anticholinergic side effects. Clinicians should generally avoid multiple medications with anticholinergic activity in the patient with dementia. Some of the common selective antimuscarinic drugs for bladder problems, (such as oxybutynin, darifenacin, trospium, fesoterodine, tolerodine, or solifenacin), do not routinely cause problems with medications used for dementia, but may cause anticholinergic side effects in some patients. Atropine may be used to offset bradycardia in cholinesterase inhibitor overdose.
    Glimepiride; Pioglitazone: (Moderate) Salicylates can indirectly increase insulin secretion. Thus, salicylates can decrease blood sugar. In large doses, salicylates can cause hyperglycemia and glycosuria.
    Glimepiride; Rosiglitazone: (Moderate) Salicylates can indirectly increase insulin secretion. Thus, salicylates can decrease blood sugar. In large doses, salicylates can cause hyperglycemia and glycosuria.
    Glipizide; Metformin: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control.
    Glucagon: (Major) The concomitant use of intravenous glucagon and anticholinergics increases the risk of gastrointestinal adverse reactions due to additive effects on inhibition of gastrointestinal motility. Concomitant use is not recommended.
    Glyburide; Metformin: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control.
    Granisetron: (Major) Because of the potential risk and severity of serotonin syndrome, use caution when administering granisetron with other drugs that have serotonergic properties such as methylene blue. If serotonin syndrome is suspected, discontinue granisetron and concurrent serotonergic agents and initiate appropriate medical treatment. Serotonin syndrome is characterized by rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death.
    Griseofulvin: (Moderate) Concurrent administration of griseofulvin with salicylates may result in decreased salicylate serum concentrations. Caution and close monitoring for changes in the effectiveness of the salicylate are recommended.
    Guaifenesin; Hydrocodone: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Guaifenesin; Hydrocodone; Pseudoephedrine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Haloperidol: (Moderate) Additive adverse effects resulting from cholinergic blockade may occur when hyoscyamine is administered concomitantly with haloperidol.
    Heparin: (Moderate) An additive risk of bleeding may be seen in patients receiving platelet inhibitors (e.g. aspirin, ASA). Despite the potential drug-drug interaction between aspirin and heparin, heparin is frequently administered in combination with low-dose aspirin therapy to patients who have had an acute myocardial infarction and in other disease states. In addition, large doses of salicylates (>= 3-4 g/day) can cause hypoprothrombinemia, an additional risk factor for bleeding.
    Homatropine; Hydrocodone: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Hyaluronidase, Recombinant; Immune Globulin: (Moderate) Immune Globulin (IG) products have been reported to be associated with renal dysfunction, acute renal failure, osmotic nephrosis, and death. Patients predisposed to acute renal failure include patients receiving known nephrotoxic drugs like nonsteroidal anti-inflammatory drugs (NSAIDs) and salicylates. Coadminister IG products at the minimum concentration available and the minimum rate of infusion practicable. Also, closely monitor renal function. (Minor) Salicylates, when given in large systemic doses, may render tissues partially resistant to the action of hyaluronidase. Patients receiving these medications may require larger amounts of hyaluronidase for equivalent dispersing effect.
    Hyaluronidase: (Minor) Salicylates, when given in large systemic doses, may render tissues partially resistant to the action of hyaluronidase. Patients receiving these medications may require larger amounts of hyaluronidase for equivalent dispersing effect.
    Hydralazine: (Moderate) Use sodium phosphates cautiously with hydralazine as concurrent use can cause hypernatremia.
    Hydralazine; Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide. (Moderate) Use sodium phosphates cautiously with hydralazine as concurrent use can cause hypernatremia.
    Hydralazine; Isosorbide Dinitrate, ISDN: (Moderate) Use sodium phosphates cautiously with hydralazine as concurrent use can cause hypernatremia.
    Hydrochlorothiazide, HCTZ: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Irbesartan: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Lisinopril: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Losartan: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Methyldopa: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide. (Moderate) Use sodium phosphates cautiously with methyldopa, as concurrent use can cause hypernatremia.
    Hydrochlorothiazide, HCTZ; Metoprolol: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Moexipril: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Olmesartan: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Propranolol: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Quinapril: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Spironolactone: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal insufficiency in patients receiving diuretics, secondary to effects on renal blood flow. Salicylates inhibit renal prostaglandin production, which causes salt and water retention and decreased renal blood flow. This combination may cause hyperkalemia. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Telmisartan: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Triamterene: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal insufficiency in patients receiving diuretics, secondary to effects on renal blood flow. Salicylates inhibit renal prostaglandin production, which causes salt and water retention and decreased renal blood flow. This combination may cause hyperkalemia. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrochlorothiazide, HCTZ; Valsartan: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Hydrocodone: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Hydrocodone; Ibuprofen: (Major) The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function. The use of salicylates together with NSAIDs can also lead to additive GI toxicity. The FDA issued an advisory that 400 mg of ibuprofen can interfere with the antiplatelet effects of low dose aspirin (81 mg per day). Routine use of ibuprofen is likely to have the most significant effect. The FDA recommends administering ibuprofen 8 hours before or 30 minutes after aspirin if concurrent therapy is needed. Interactions have been noted between ibuprofen and aspirin, ASA. Concurrent use of chronic ibuprofen therapy (800 mg three times daily) seems to antagonize the inhibition of platelet cyclooxygenase (COX)-1 activity and impairment of platelet aggregation by low-dose aspirin (81 mg once daily) per an ex vivo analysis. In this study, diclofenac or rofecoxib therapy, agents with less activity at COX-1 than ibuprofen, did not affect inhibition of platelet aggregation by aspirin. An in vitro study has shown that the antagonism of aspirin platelet inhibition probably involves competition at platelet-derived COX-1 and is related to the NSAIDs' ability to inhibit COX-1 mediated thromboxane B2 production in platelets. Clinically, the interaction may be more dramatic with regular as compared with intermittent ibuprofen usage. Quantification of the risk was determined by the analysis of retrospective data, which may be inaccurate and incomplete. However, a trend towards a greater risk of a second myocardial infarction in the year after the initial event among adults taking daily aspirin was associated with a greater length of ibuprofen exposure. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Hydrocodone; Phenylephrine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Hydrocodone; Potassium Guaiacolsulfonate: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Hydrocodone; Potassium Guaiacolsulfonate; Pseudoephedrine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Hydrocodone; Pseudoephedrine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydrocodone is used concomitantly with an anticholinergic drug. The concomitant use of hydrocodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Hydrocortisone: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Hydromorphone: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when hydromorphone is used concomitantly with an anticholinergic drug. The concomitant use of hydromorphone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Hydroxyzine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Ibuprofen: (Major) The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function. The use of salicylates together with NSAIDs can also lead to additive GI toxicity. The FDA issued an advisory that 400 mg of ibuprofen can interfere with the antiplatelet effects of low dose aspirin (81 mg per day). Routine use of ibuprofen is likely to have the most significant effect. The FDA recommends administering ibuprofen 8 hours before or 30 minutes after aspirin if concurrent therapy is needed. Interactions have been noted between ibuprofen and aspirin, ASA. Concurrent use of chronic ibuprofen therapy (800 mg three times daily) seems to antagonize the inhibition of platelet cyclooxygenase (COX)-1 activity and impairment of platelet aggregation by low-dose aspirin (81 mg once daily) per an ex vivo analysis. In this study, diclofenac or rofecoxib therapy, agents with less activity at COX-1 than ibuprofen, did not affect inhibition of platelet aggregation by aspirin. An in vitro study has shown that the antagonism of aspirin platelet inhibition probably involves competition at platelet-derived COX-1 and is related to the NSAIDs' ability to inhibit COX-1 mediated thromboxane B2 production in platelets. Clinically, the interaction may be more dramatic with regular as compared with intermittent ibuprofen usage. Quantification of the risk was determined by the analysis of retrospective data, which may be inaccurate and incomplete. However, a trend towards a greater risk of a second myocardial infarction in the year after the initial event among adults taking daily aspirin was associated with a greater length of ibuprofen exposure.
    Ibuprofen; Oxycodone: (Major) Serotonin syndrome can occur during concomitant use of opiate agonists with serotonergic drugs, such as methylene blue. Symptoms may occur hours to days after concomitant use, particularly after dose increases. Serotonin syndrome may occur within recommended dose ranges. If concomitant treatment is clinically warranted, careful observation of the patient is advised, especially during initiation of the second therapy and after dosage increases of either agent. Instruct patients to immediately report symptoms of agitation, hallucinations, tachycardia, fever, excessive sweating, shivering or shaking, muscle twitching or stiffness, trouble with coordination, nausea, vomiting, or diarrhea. (Major) The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function. The use of salicylates together with NSAIDs can also lead to additive GI toxicity. The FDA issued an advisory that 400 mg of ibuprofen can interfere with the antiplatelet effects of low dose aspirin (81 mg per day). Routine use of ibuprofen is likely to have the most significant effect. The FDA recommends administering ibuprofen 8 hours before or 30 minutes after aspirin if concurrent therapy is needed. Interactions have been noted between ibuprofen and aspirin, ASA. Concurrent use of chronic ibuprofen therapy (800 mg three times daily) seems to antagonize the inhibition of platelet cyclooxygenase (COX)-1 activity and impairment of platelet aggregation by low-dose aspirin (81 mg once daily) per an ex vivo analysis. In this study, diclofenac or rofecoxib therapy, agents with less activity at COX-1 than ibuprofen, did not affect inhibition of platelet aggregation by aspirin. An in vitro study has shown that the antagonism of aspirin platelet inhibition probably involves competition at platelet-derived COX-1 and is related to the NSAIDs' ability to inhibit COX-1 mediated thromboxane B2 production in platelets. Clinically, the interaction may be more dramatic with regular as compared with intermittent ibuprofen usage. Quantification of the risk was determined by the analysis of retrospective data, which may be inaccurate and incomplete. However, a trend towards a greater risk of a second myocardial infarction in the year after the initial event among adults taking daily aspirin was associated with a greater length of ibuprofen exposure. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when oxycodone is used concomitantly with an anticholinergic drug. The concomitant use of oxycodone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Ibuprofen; Pseudoephedrine: (Major) The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function. The use of salicylates together with NSAIDs can also lead to additive GI toxicity. The FDA issued an advisory that 400 mg of ibuprofen can interfere with the antiplatelet effects of low dose aspirin (81 mg per day). Routine use of ibuprofen is likely to have the most significant effect. The FDA recommends administering ibuprofen 8 hours before or 30 minutes after aspirin if concurrent therapy is needed. Interactions have been noted between ibuprofen and aspirin, ASA. Concurrent use of chronic ibuprofen therapy (800 mg three times daily) seems to antagonize the inhibition of platelet cyclooxygenase (COX)-1 activity and impairment of platelet aggregation by low-dose aspirin (81 mg once daily) per an ex vivo analysis. In this study, diclofenac or rofecoxib therapy, agents with less activity at COX-1 than ibuprofen, did not affect inhibition of platelet aggregation by aspirin. An in vitro study has shown that the antagonism of aspirin platelet inhibition probably involves competition at platelet-derived COX-1 and is related to the NSAIDs' ability to inhibit COX-1 mediated thromboxane B2 production in platelets. Clinically, the interaction may be more dramatic with regular as compared with intermittent ibuprofen usage. Quantification of the risk was determined by the analysis of retrospective data, which may be inaccurate and incomplete. However, a trend towards a greater risk of a second myocardial infarction in the year after the initial event among adults taking daily aspirin was associated with a greater length of ibuprofen exposure.
    Imipramine: (Severe) According to the manufacturer, treatment initiation with imipramine is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than imipramine (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving imipramine and requiring urgent treatment with IV methylene blue, imipramine should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 2 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Imipramine may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent, in patients receiving serotonergic agents. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma.
    Immune Globulin IV, IVIG, IGIV: (Moderate) Immune Globulin (IG) products have been reported to be associated with renal dysfunction, acute renal failure, osmotic nephrosis, and death. Patients predisposed to acute renal failure include patients receiving known nephrotoxic drugs like nonsteroidal anti-inflammatory drugs (NSAIDs) and salicylates. Coadminister IG products at the minimum concentration available and the minimum rate of infusion practicable. Also, closely monitor renal function.
    Incretin Mimetics: (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents. Monitor blood glucose closely during coadministration.
    Indapamide: (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics because salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance.
    Indomethacin: (Major) The concurrent use of salicylates and indomethacin is not recommended. Combined use does not produce any greater therapeutic effect than indomethacin monotherapy. Also, a significantly greater incidence of gastrointestinal adverse effects with concurrent use has been observed. Because NSAIDs can cause GI bleeding, inhibit platelet aggregation, and prolong bleeding time, additive effects may be seen in patients receiving platelet inhibitors (e.g., aspirin), anticoagulants, or thrombolytic agents.
    Insulins: (Moderate) Use large doses of aspirin cautiously in patients receiving insulin. Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia.
    Ipratropium: (Moderate) Although ipratropium is minimally absorbed into the systemic circulation after inhalation, there is the potential for tiotropium to have additive anticholinergic effects when administered with other antimuscarinics. Per the manufaturer, avoid concomitant administration of ipratropium with other anticholinergic medications, such as antimucarinics.
    Isocarboxazid: (Severe) Concurrent use of methylene blue and MAOIs (e.g., tranylcypromine, isocarboxazid, phenelzine, and including selective MAOIs such as selegiline, rasagiline) should generally be avoided due to the potential for serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and traditional MAOIs similarly increase central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonergic agents. It is not known if patients receiving intravenous methylene blue with MAO-inhibiting agents or linezolid are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. If emergent treatment with methylene blue is required in a patient receiving an MAOI, the MAOI should be stopped immediately and the patient should be monitored for symptoms of CNS toxicity for two weeks or until 24 hours after the last dose of methylene blue, whichever comes first. During non-emergent use of methylene blue, the MAOI should be stopped at least 2 weeks prior to methylene blue treatment. Because rasagiline is a selective monoamine oxidase-B (MAO-B) inhibitor at manufacturer recommended doses, an interaction with serotonin-enhancing medications may be less likely to occur than with other traditional MAO inhibitors.
    Isoniazid, INH: (Major) Concurrent use of methylene blue and drugs that possess MAOI-like activity (e.g., isoniazid, INH) should generally be avoided due to the potential for serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A). Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving serotonergic agents such as selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clompiramine. It is not known if patients receiving intravenous methylene blue with other serotonergic psychiatric agents are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Isoniazid, INH; Pyrazinamide, PZA; Rifampin: (Major) Concurrent use of methylene blue and drugs that possess MAOI-like activity (e.g., isoniazid, INH) should generally be avoided due to the potential for serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A). Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving serotonergic agents such as selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clompiramine. It is not known if patients receiving intravenous methylene blue with other serotonergic psychiatric agents are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Isoniazid, INH; Rifampin: (Major) Concurrent use of methylene blue and drugs that possess MAOI-like activity (e.g., isoniazid, INH) should generally be avoided due to the potential for serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A). Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving serotonergic agents such as selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clompiramine. It is not known if patients receiving intravenous methylene blue with other serotonergic psychiatric agents are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Itraconazole: (Moderate) Antimuscarinics can raise intragastric pH. This effect may decrease the oral bioavailability of itraconazole; antimuscarinics should be used cautiously in patients receiving itraconazole.
    Ketoprofen: (Major) The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function. The use of salicylates together with NSAIDs can also lead to additive GI toxicity.
    Ketorolac: (Severe) Increased adverse gastrointestinal and other effects are possible if ketorolac is used with salicylates. In addition, concomitant administration of salicylates and ketorolac has resulted in a reduction in protein binding and a two-fold increase in unbound plasma concentrations of ketorolac. As a result, concomitant use of ketorolac and aspirin or any other NSAID is contraindicated. Because ketorolac can cause GI bleeding, inhibit platelet aggregation, and may prolong bleeding time, additive effects may be seen in patients receiving platelet inhibitors (e.g., aspirin), anticoagulants, or thrombolytic agents.
    Lansoprazole; Naproxen: (Major) Aspirin, ASA displaces naproxen from binding to albumin and increases naproxen excretion. Due to an increased free fraction of naproxen, increased adverse gastrointestinal effects are possible if naproxen is used with aspirin. In addition, further benefit with use of the two drugs as compared with aspirin monotherapy is not apparent, and antagonism of the irreversible platelet effect of aspirin occurs with concurrent use. The interaction appears to be due to competition at the enzyme active site. Patients who take low-dose aspirin for cardiovascular health may have the beneficial effects of aspirin on platelet function counteracted by naproxen. Concomitant aspirin and naproxen use is not recommended. The use of Naproxen with other salicylates can also lead to additive GI toxicity.
    Levocetirizine: (Moderate) Dry mouth and drowsiness were more common in patients receiving cetirizine/levocetirizine vs. placebo, and caution may be necessary during concomitant use of cetirizine/levocetirizine with the antimuscarinics.
    Levodopa: (Minor) Through its central antimuscarinic actions, hyoscyamine can potentiate the dopaminergic effects of levodopa. Clinicians should be ready to decrease doses of levodopa if hyoscyamine is added.
    Levomilnacipran: (Severe) Concurrent use of methylene blue and serotonin norepinephrine reuptake inhibitors (SNRIs) (e.g., venlafaxine, duloxetine, desvenlafaxine, milnacipran) should generally be avoided due to the potential for serotonin syndrome. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin; therefore, concurrent use of an MAO-A inhibitor with serotonergic agents such as SNRIs may result in a clinically significant interaction. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, SNRIs, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. One case report suggests that serotonin toxicity may have occurred post-operatively following administration of standard infusions of methylene blue in a patient receiving duloxetine. The patient experienced disorientation, a mildly elevated temperature, tachycardia, elevated blood pressure, mild agitation, and nystagmus. In a separate case, a patient who had been receiving venlafaxine developed expressive aphasia, confusion, and disinhibition following a methylene blue infusion. The authors concluded that methylene blue toxicity had occurred; however, they did not exclude the possibility of a drug interaction based upon previous reports of an interaction between injectable methylene blue and selective serotonin reuptake inhibitors (SSRIs). Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma. If emergent treatment with methylene blue is required in a patient receiving an SNRI, the SNRI must be stopped immediately and the patient should be monitored for symptoms of CNS toxicity for two weeks or until 24 hours after the last dose of methylene blue, whichever comes first. During non-emergent use of methylene blue, the SNRI should be stopped at least 2 weeks prior to methylene blue treatment, but also taking into consideration the half-life of the SNRI being discontinued.
    Levorphanol: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when levorphanol is used concomitantly with an anticholinergic drug. The concomitant use of levorphanol and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Linaclotide: (Moderate) Anticholinergics can promote constipation and pharmacodynamically oppose the action of drugs used for the treatment of constipation, such as linaclotide. The clinical significance of these potential interactions is uncertain.
    Linagliptin: (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents, such as linagliptin.
    Linagliptin; Metformin: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control. (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood glucose concentrations. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents, such as linagliptin.
    Linezolid: (Major) Concurrent use of methylene blue and medications with serotonergic effects, such as linezolid, should be avoided if possible. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and linezolid is an antibiotic with reversible, non-selective MAO inhibitor activity. Since MAO type A deaminates serotonin, administration of linezolid concurrently with another agent with MAO-A inhibiting activity can potentially increase serotonin. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonergic agents. It is not known if patients receiving intravenous methylene blue with linezolid are at a comparable risk. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Lisdexamfetamine: (Severe) Amphetamines should not be administered during or within 14 days after the use of methylene blue. Methylene blue is a potent, reversible monoamine oxidase inhibitor (MAOI) which can prolong and intensify the cardiac stimulation and vasopressor effects of amphetamines, potentially resulting in hypertensive crisis. Methylene blue also has the potential to interact with serotonergic agents, such as amphetamines, which may increase the risk for serotonin syndrome. Serotonin syndrome is characterized by mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea), and in rare instances, death. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents, such as amphetamines, with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. (Major) Concurrent use of urinary acidifying agents, such as methenamine salts (e.g., methenamine containing urinary products) and lisdexamfetamine should be avoided if possible. Urinary acidifying agents reduce the tubular reabsorption of amphetamines. As a result, amphetamine clearance is accelerated and the duration of effect is reduced. If combination therapy is necessary, adjust the lisdexamfetamine dose according to clinical response as needed.
    Lisinopril: (Moderate) Aspirin, ASA may reduce the vasodilatory efficacy of ACE inhibitors by inhibiting the synthesis of vasodilatory prostaglandins. This interaction has been documented primarily in heart failure patients. However, the established benefits of using aspirin in combination with an ACE inhibitor in patients with ischemic heart disease and left ventricular dysfunction generally outweigh this concern. Patients receiving concurrent salicylates and ACE inhibitor therapy should be monitored for antihypertensive or vasodilatory efficacy; the dose of the ACE inhibitor can be adjusted if indicated based on clinical evaluation.
    Lithium: (Major) Theoretically, concurrent use of methylene blue and lithium may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and lithium is thought to increase central serotonin effects by various mechanisms. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other psychiatric serotonergic agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. If serotonin syndrome is suspected, serotonergic agents should be discontinued and appropriate medical treatment should be implemented.
    Loop diuretics: (Moderate) Salicylates may decrease the diuretic, natriuretic, and antihypertensive actions of diuretics, possibly through inhibition of renal prostaglandin synthesis. Patients receiving loop diuretics and salicylates should be monitored for changes in the effectiveness of their diuretic therapy.
    Loperamide: (Moderate) Loperamide decreases GI motility. Agents that inhibit intestinal motility or prolong intestinal transit time have been reported to induce toxic megacolon. Other drugs that also decrease GI motility may produce additive effects with loperamide if used concomitantly. These include therapeutic doses of common systemic antimuscarinics (e.g., hyoscyamine). Additive GI and CNS actions and may lead to undesirable side effects in some patients.
    Loperamide; Simethicone: (Moderate) Loperamide decreases GI motility. Agents that inhibit intestinal motility or prolong intestinal transit time have been reported to induce toxic megacolon. Other drugs that also decrease GI motility may produce additive effects with loperamide if used concomitantly. These include therapeutic doses of common systemic antimuscarinics (e.g., hyoscyamine). Additive GI and CNS actions and may lead to undesirable side effects in some patients.
    Lorcaserin: (Major) Theoretically, concurrent use of methylene blue and lorcaserin may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and lorcaserin increases central serotonin effects). Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Low Molecular Weight Heparins: (Moderate) An additive risk of bleeding may be seen in patients receiving a low molecular weight heparin in combination with other agents known to increase the risk of bleeding such as salicylates. Monitor clinical and laboratory response closely during concurrent use.
    Lubiprostone: (Moderate) Antimuscarinic drugs can promote constipation and pharmacodynamically oppose the action of drugs used for the treatment of constipation, such as lubiprostone. The clinical significance of these potential interactions is uncertain.
    Lurasidone: (Moderate) Antipsychotic agents may disrupt core temperature regulation; therefore, caution is recommended during concurrent use of lurasidone and medications with anticholinergic activity such as antimuscarinics. Concurrent use of lurasidone and medications with anticholinergic activity may contribute to heat-related disorders. Monitor patients for heat intolerance, decreased sweating, or increased body temperature if lurasidone is used with antimuscarinics.
    Magnesium Hydroxide: (Major) Aluminum hydroxide and magnesium hydroxide (as well as other antacids, i.e. aluminum hydroxide; magnesium carbonate, aluminum hydroxide; magaldrate; magnesium hydroxide, and aluminum hydroxide; magnesium trisilicate) may interact with urinary acidifiers by alkalinizing the urine. Frequent use of these high dose antacids should be avoided in patients receiving urinary acidifiers. (Major) The therapeutic action of methenamine requires an acidic urine. Antacids containing alkalinizing agents such as sodium bicarbonate can alkalinize the urine, thereby decreasing the effectiveness of methenamine by increasing the amount of non-ionized drug available for renal tubular reabsorption. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended. (Moderate) Antacids may inhibit the oral absorption of anticholinergics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction.
    Magnesium Salicylate: (Moderate) Acidification of the urine may increase serum concentrations of salicylates by increasing tubular reabsorption of salicylates, however, this interaction is not likely to be clinically significant since the urine is normally acidic.
    Maprotiline: (Severe) According to the manufacturer, treatment initiation with maprotiline is contraindicated in patients currently receiving intravenous (IV) methylene blue due to an increased risk of serotonin syndrome. If urgent psychiatric treatment is required, interventions other than maprotiline (e.g., alternative medication, hospitalization) should be considered. Conversely, in patients receiving maprotiline and requiring urgent treatment with IV methylene blue, maprotiline should be discontinued immediately and methylene blue therapy initiated only if acceptable alternatives are not available and the potential benefits outweigh the risks. The patient should be monitored for serotonin syndrome for 2 weeks or until 24 hours after the last dose of methylene blue, whichever comes first. Maprotiline may be re-initiated 24 hours after the last dose of methylene blue. Results from an in vitro study indicate that methylene blue is a potent, reversible inhibitor of the monoamine oxidase type A enzyme (MAO-A). MAO-A is responsible for the metabolism of serotonin. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent, in patients receiving serotonergic agents. It is not known if patients receiving other serotonergic psychiatric agents with IV methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between IV methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Signs and symptoms of serotonin syndrome include fever, diaphoresis, shivering, myoclonus, tremor, tachycardia, diarrhea, nausea, headache, incoordination, mental status changes (e.g., agitation, confusion), hyperreflexia, seizures, and coma. (Moderate) Additive anticholinergic effects may be seen when hyoscyamine is used concomitantly with other drugs with moderate to significant anticholinergic effects including maprotiline. Clinicians should note that antimuscarinic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation.
    Measles Virus; Mumps Virus; Rubella Virus; Varicella Virus Vaccine, Live: (Major) No adverse events associated with the use of salicylates after varicella vaccination have been reported. However, the manufacturer of varicella virus vaccine live recommends the avoidance of salicylates or aspirin, ASA use for 6 weeks after vaccination. Reye's syndrome, which exclusively affects children under 15 years old, has been associated with aspirin use following active varicella infection. Vaccination with close clinical monitoring is recommended for children who require therapeutic aspirin, ASA therapy; according to the CDC the use of attenuated, live varicella virus vaccine is thought to present less risk than natural varicella disease to such children.
    Meclizine: (Moderate) The anticholinergic effects of sedating H1-blockers may be enhanced when combined with other antimuscarinics. Clinicians should note that anticholinergic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness may also occur when antimuscarinics are combined with sedating antihistamines.
    Meclofenamate Sodium: (Major) The concurrent use of aspirin with other NSAIDs should be avoided because this may increase bleeding or lead to decreased renal function. The use of salicylates together with NSAIDs can also lead to additive GI toxicity.
    Mefenamic Acid: (Major) Increased adverse gastrointestinal (GI) effects are possible if mefenamic acid is used with salicylates. In addition, concomitant administration of salicylates and mefenamic acid may result in an increase in unbound plasma concentrations of either drug, which could result in greater adverse effects. In general, concomitant use of aspirin and mefenamic acid is not recommended.
    Meglitinides: (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood sugar and may potentiate the effects of antidiabetic agents. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose or use of greater than maximum recommended daily dosages, salicylates can cause either hypoglycemia or hyperglycemia. Large doses of aspirin should be used cautiously in patients who receive antidiabetic agents.
    Meloxicam: (Major) Additive adverse gastrointestinal (GI) effects are possible if meloxicam is used with salicylates (e.g., aspirin). The concurrent use of aspirin and a nonsteroidal anti-inflammatory drug (NSAID) does increase the risk of serious gastrointestinal events. Concomitant administration of aspirin, ASA (3000 mg/day) to healthy volunteers increased the meloxicam AUC by 10% and increased the meloxicam peak plasma concentrations by 24%. Because of its lack of platelet effects, meloxicam is not a substitute for aspirin for cardiovascular prophylaxis.
    Memantine: (Moderate) The adverse effects of anticholinergics, such as dry mouth, urinary hesitancy or blurred vision may be enhanced with use of memantine; dosage adjustments of the anticholinergic drug may be required when memantine is coadministered. In addition, preliminary evidence indicates that chronic anticholinergic use in patients with Alzheimer's Disease may possibly have an adverse effect on cognitive function. Therefore, the effectiveness of drugs used in the treatment of Alzheimer's such as memantine, may be adversely affected by chronic antimuscarinic therapy.
    Meperidine: (Severe) Meperidine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Severe reactions including coma, severe respiratory depression, cyanosis, and hypotension have occurred; some reactions have been fatal. The mechanism of these reactions is unclear; however, it may be related to a preexisting hyperphenylalaninemia. Concomitant use of meperidine with other serotonergic drugs such as MAOIs may result in serotonin syndrome with excitation; sweating; rigidity; hypertension; severe respiratory depression; coma; and circulatory collapse, possibly resulting in death. Intravenous hydrocortisone or prednisolone has been used to treat severe reactions, with the addition of intravenous chlorpromazine in cases exhibiting hypertension and hyperpyrexia. The usefulness and safety of opiate antagonists in the treatment of these reactions is unknown. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when meperidine is used concomitantly with an anticholinergic drug. The concomitant use of meperidine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Meperidine; Promethazine: (Severe) Meperidine use is contraindicated in patients who are receiving or who have received monoamine oxidase inhibitors (MAOIs) within the previous 14 days. Methylene blue is a reversible inhibitor of MAO. Severe reactions including coma, severe respiratory depression, cyanosis, and hypotension have occurred; some reactions have been fatal. The mechanism of these reactions is unclear; however, it may be related to a preexisting hyperphenylalaninemia. Concomitant use of meperidine with other serotonergic drugs such as MAOIs may result in serotonin syndrome with excitation; sweating; rigidity; hypertension; severe respiratory depression; coma; and circulatory collapse, possibly resulting in death. Intravenous hydrocortisone or prednisolone has been used to treat severe reactions, with the addition of intravenous chlorpromazine in cases exhibiting hypertension and hyperpyrexia. The usefulness and safety of opiate antagonists in the treatment of these reactions is unknown. (Moderate) Additive anticholinergic effects may be seen when anticholinergics are used concomitantly with phenothiazines, including promethazine. Clinicians should note that antimuscarinic effects may be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. Additive drowsiness or other additive CNS effects may also occur. (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when meperidine is used concomitantly with an anticholinergic drug. The concomitant use of meperidine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
    Metformin: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control.
    Metformin; Pioglitazone: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control. (Moderate) Salicylates can indirectly increase insulin secretion. Thus, salicylates can decrease blood sugar. In large doses, salicylates can cause hyperglycemia and glycosuria.
    Metformin; Repaglinide: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control. (Moderate) Salicylates, by inhibiting prostaglandin E2 synthesis, can indirectly increase insulin secretion. Thus, salicylates can decrease blood sugar and may potentiate the effects of antidiabetic agents. In large doses, salicylates uncouple oxidative phosphorylation, deplete hepatic and muscle glycogen, and cause hyperglycemia and glycosuria. After acute overdose or use of greater than maximum recommended daily dosages, salicylates can cause either hypoglycemia or hyperglycemia. Large doses of aspirin should be used cautiously in patients who receive antidiabetic agents.
    Metformin; Rosiglitazone: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control. (Moderate) Salicylates can indirectly increase insulin secretion. Thus, salicylates can decrease blood sugar. In large doses, salicylates can cause hyperglycemia and glycosuria.
    Metformin; Saxagliptin: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control. (Moderate) Salicylates can indirectly increase insulin secretion, decreasing blood glucose concentrations. In large doses, salicylates may cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving saxagliptin.
    Metformin; Sitagliptin: (Moderate) Large doses of salicylates may enhance hypoglycemia in diabetic patients via inhibition of prostaglandin synthesis. If these agents are administered or discontinued in patients receiving oral antidiabetic agents, patients should be monitored for hypoglycemia or loss of blood glucose control. (Moderate) Salicylates can indirectly increase insulin secretion, decreasing blood glucose concentrations. In large doses, salicylates may cause hyperglycemia and glycosuria. After acute overdose, aspirin can cause either hypo- or hyperglycemia. Large doses of aspirin should be used cautiously in patients receiving antidiabetic agents.
    Methadone: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when methadone is used concomitantly with an anticholinergic drug. The concomitant use of methadone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Minor) As methadone is a weak base, the renal elimination of methadone is increased by urine acidification. Thus acidifying agents may lower the serum methadone concentration. The limited amounts of circulating methadone that undergo glomerular filtration are partially reabsorbed by the kidney tubules, and this reabsorption is pH-dependent. Several studies have demonstrated that methadone is cleared faster from the body with an acidic urinary pH as compared with a more basic pH.
    Methamphetamine: (Severe) Amphetamines should not be administered during or within 14 days after the use of methylene blue. Methylene blue is a potent, reversible monoamine oxidase inhibitor (MAOI) which can prolong and intensify the cardiac stimulation and vasopressor effects of amphetamines, potentially resulting in hypertensive crisis. Methylene blue also has the potential to interact with serotonergic agents, such as amphetamines, which may increase the risk for serotonin syndrome. Serotonin syndrome is characterized by mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea), and in rare instances, death. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents, such as amphetamines, with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. (Major) Methenamine and methenamine salts (e.g., methenamine; sodium acid phosphate) are urinary acidifiers, and acidic urine will significantly decrease the half-life of methamphetamine. Urinary acidifying agents increase the concentration of the ionized species of the amphetamine molecule, which increases urinary excretion.
    Methazolamide: (Major) Avoid the coadministration of high-dose salicylates and carbonic anhydrase inhibitors, like methazolamide, whenever possible. The combination yielded reports of anorexia, tachypnea, lethargy, metabolic acidosis, coma, and death. The mechanism appears to be accumulation of the carbonic anhydrase inhibitor, resulting in increased CNS depression and metabolic acidosis. The acidosis may allow greater CNS penetration of the salicylate. (Major) The therapeutic action of methenamine requires an acidic urine. Methazolamide can alkalinize the urine, thereby decreasing the effectiveness of methenamine by increasing the amount of non-ionized drug available for renal tubular reabsorption. Increased urine alkalinity also can inhibit the conversion of methenamine to formaldehyde, which is the active bacteriostatic form; concurrent use of methenamine and urinary alkalizers is not recommended.
    Methotrexate: (Severe) Caution should be exercised when salicylates are given in combination with methotrexate. Since both are weak acids, salicylates can impair the renal secretion of methotrexate and increase the risk of methotrexate toxicity. Salicylates can also displace methotrexate from protein-binding sites. Although the risk for drug interactions with methotrexate is greatest during high-dose methotrexate therapy, it has been recommended that any of these drugs be used cautiously with methotrexate even when methotrexate is used in low doses for the treatment of rheumatoid arthritis. A significantly higher incidence of leukopenia has been reported in patients taking aspirin during methotrexate therapy. In addition, large doses of salicylates (>= 3 to 4 g/day) can cause hypoprothrombinemia, an additional risk factor for bleeding.
    Methoxsalen: (Moderate) Use methoxsalen and methylene blue together with caution; the risk of severe burns/photosensitivity may be additive. If concurrent use is necessary, closely monitor patients for signs or symptoms of skin toxicity.
    Methyclothiazide: (Major) Thiazide diuretics may cause the urine to become alkaline. This may reduce the effectiveness of methenamine by inhibiting its conversion to formaldehyde. (Moderate) Salicylates can increase the risk of renal toxicity in patients receiving diuretics. Salicylates inhibit renal prostaglandin synthesis, which can lead to fluid retention and increased peripheral vascular resistance. Salicylates may decrease the hyperuricemic effect of hydrochlorothiazide.
    Methyldopa: (Moderate) Use sodium phosphates cautiously with methyldopa, as concurrent use can cause hypernatremia.
    Methylergonovine: (Moderate) Theoretically, concurrent use of methylene blue and ergot alkaloids may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and ergot alkaloids increase central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Methylphenidate: (Moderate) Theoretically, concurrent use of methylene blue and methylphenidate may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and methylphenidate increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by the rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death. If serotonin syndrome occurs, all serotonergic agents should be discontinued and appropriate medical management should be implemented.
    Methylprednisolone: (Moderate) Use sodium phosphate cautiously with corticosteroids, especially mineralocorticoids or corticotropin, ACTH, as concurrent use can cause hypernatremia.
    Methysergide: (Moderate) Theoretically, concurrent use of methylene blue and ergot alkaloids may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a