PDR MEMBER LOGIN:
  • PDR Search

    Required field
  • Advertisement
  • CLASSES

    Antimuscarinics

    DEA CLASS

    Rx, OTC

    DESCRIPTION

    Tertiary amine with antimuscarinic and antispasmodic actions
    Used for neurogenic bladder and to reduce urinary incontinence
    Oral, topical, and transdermal dosage forms available

    COMMON BRAND NAMES

    Ditropan, Ditropan XL, Gelnique, Oxytrol, Oxytrol for Women

    HOW SUPPLIED

    Ditropan XL/Oxybutynin/Oxybutynin Chloride Oral Tab ER: 5mg, 10mg, 15mg
    Ditropan/Oxybutynin/Oxybutynin Chloride Oral Sol: 5mg, 5mL
    Ditropan/Oxybutynin/Oxybutynin Chloride Oral Tab: 5mg
    Gelnique Transdermal Gel: 10%
    Oxybutynin/Oxybutynin Chloride Oral Syrup: 5mg, 5mL
    Oxytrol/Oxytrol for Women Transdermal Film ER: 3.9mg, 24h

    DOSAGE & INDICATIONS

    For the treatment of an overactive bladder (OAB) with symptoms of urinary frequency, urinary urgency, or urinary incontinence due to involuntary detrusor muscle contractions (includes neurogenic bladder).
    Oral dosage (immediate-release dosage forms)
    Adults

    The usual dose is 5 mg PO 2—3 times per day. The maximum dose is 5 mg PO 4 times per day.

    Geriatric

    See adult dosage. A lower starting dose of 2.5 mg PO 2—3 times a day is recommended for frail geriatric patients. In one study, 2.5 mg PO twice daily was used initially, and increased to a maximum of 5 mg PO three times per day, if tolerated in geriatric patients. Oxybutynin did reduce daytime urinary frequency, but its ability to reduce the number of incontinent episodes was no better than placebo. Subjectively, the patients reported a preference for oxybutynin compared to placebo.

    Adolescents

    The recommended dose is 5 mg PO 2—4 times per day.

    Children >= 5 years

    Usual dose: 5 mg PO twice daily. The maximum recommended dose is 5 mg PO three times per day. Safety and efficacy have been demonstrated for patients 5 years of age and older.

    Children† < 5 years

    Initially, 0.2 mg/kg/day PO, given in divided doses. The usual weight-based dose range is 0.2 mg/kg/day to 0.4 mg/kg/day PO, given in three divided doses.

    Oral dosage (extended-release tablets, e.g., Ditropan XL)
    Adults, including Geriatric patients

    Initially, 5—10 mg PO once daily. Dosage may be adjusted weekly by 5-mg increments based on efficacy and tolerability. Maximum: 30 mg/day PO. The rate and severity of anticholinergic effects reported by adults younger than 65 years and geriatric adults were similar in clinical trials for Ditropan XL.

    Children and Adolescents >= 6 years

    Initially, 5 mg PO once daily. Dosage may be adjusted weekly by 5-mg increments based on efficacy and tolerability. Maximum: 20 mg/day PO. Indicated for the treatment of pediatric patients aged 6 years and older with symptoms of detrusor overactivity associated with a neurological condition (e.g., spina bifida).

    Transdermal dosage (Oxytrol transdermal patch)
    Adults

    Apply one 39 cm2 patch (delivering 3.9 mg/day of oxybutynin) topically twice weekly (every 3—4 days) to the abdomen, hip, or buttock. Rotate patch site at each application. NOTE: Only approved for nonprescription (OTC) treatment of overactive bladder in women aged 18 years and older; the transdermal patch will remain available for men by prescription only.

    Children† >= 6 years and Adolescents†

    Further study is needed to establish safety and efficacy in pediatric patients; for use by prescription only. In one open pilot study, 35 children (mean age: 8 years, range: 4 to 16 years) with non-neuropathic (idiopathic) overactive bladder (OAB) received one Oxytrol patch (delivering 3.9 mg/day of oxybutynin) topically twice weekly (every 3 to 4 days) as per the marketed product instructions; sites were rotated with each application. Most (97%) patients reported good symptom response. The main side effect was skin irritation (35%), leading to patch discontinuation in 20%. There were no reports of other significant side effects.

    Topical dosage (oxybutynin 3% topical gel, e.g., Gelnique 3%, Anturol 3%)
    Adults

    Apply 3 pumps (84 mg/day) topically once daily. Apply to clean, dry, intact skin on the abdomen, upper arms/shoulders, or thighs. Rotate sites to avoid local irritation.

    Topical dosage (Gelnique 10% topical gel)
    Adults

    Apply the contents of one 10% gel packet topically once daily. Apply to the abdomen, upper arms/shoulders, or thighs; rotate sites of application - the same site should not be used on consecutive days. Each packet contains 100 mg oxybutynin.

    MAXIMUM DOSAGE

    Adults

    20 mg/day PO for immediate-release dosage forms; 30 mg/day PO for extended-release Ditropan XL.

    Geriatric

    20 mg/day PO for immediate-release dosage forms; 30 mg/day PO for extended-release Ditropan XL.

    Adolescents

    15—20 mg/day PO for immediate-release dosage forms; 20 mg/day PO for extended-release Ditropan XL.

    Children

    >= 6 years: 15 mg/day PO for immediate-release dosage forms; 20 mg/day PO for extended-release Ditropan XL.
    5 years: 15 mg/day PO for immediate-release dosage forms.
    1—4 years: Safety and efficacy have not been established.

    DOSING CONSIDERATIONS

    Hepatic Impairment

    No specific recommendations are available; lower dosages may be needed in hepatic disease because the drug is extensively metabolized in the liver. Adjust dosage based on clinical response. Extended-release formulations of oxybutynin have not been evaluated and are not recommended.

    Renal Impairment

    Specific guidelines for dosage adjustments in renal impairment are not available; however, it appears no dosage adjustment would be needed. Extended-release formulations of oxybutynin have not been evaluated in patients with severe renal impairment.

    ADMINISTRATION

    Oral Administration

    May be administered on an empty stomach. To prevent gastric irritation, give with meals or milk.

    Oral Solid Formulations

    Extended release tablets: Administer at roughly the same time each day. Swallow whole with a sip of liquid; do not crush, chew, or divide. The biologically inert portions of the Ditropan XL tablet remain intact during intestinal transit and may be visible in the stool.

    Oral Liquid Formulations

    Oral solution: Measure dosage with a calibrated oral dosage device.

    Topical Administration
    Transdermal Patch Formulations

    Apply to clean, dry skin on the abdomen, hip, or buttock. Avoid applying to areas with cuts, calluses, scars, oil, burns, or irritation. Rotate application site, avoiding re-application to the same site within 7 days.
    Use firm pressure over patch for 10 seconds to ensure contact with skin, especially around the edges. If patch becomes loose or falls off, replace with another one. Do not cut or trim patch.
    Patches should not be affected by showering or bathing.

    Other Topical Formulations

    Topical Gel Formulations
    Apply topically only. Do not ingest. Before and after application, wash hands thoroughly with soap and water.
    Apply to clean, dry skin on the abdomen, upper arms/shoulders, or thighs. If applying to the abdomen, avoid the navel. Also avoid applying to areas with cuts, calluses, scars, oil, burns, irritation or recently shaven. Rotate application site, avoiding use of the same site on consecutive days.
    Gelnique 10% Topical Gel: Squeeze the entire contents of 1 packet to deliver dose (100 mg) into the palm of the hand or directly onto the application site. Gently rub the gel into your skin until it is dried.
    Anturol 3% Topical Gel: Fully depress pump 3 times to deliver dose (84 mg) into the palm of the hand or directly onto the application site. Apply immediately after actuating the dose. Gently rub the gel into your skin until it is dried.
    For one hour after application, avoid bathing, swimming, showering, exercising or immersing the application site in water. Allow the site to dry a few minutes before putting on clothing.
    If direct skin-to-skin contact with another person is expected, the application site should be covered with clothing once the gel has dried. If someone else is exposed to the gel or the application area, that person should wash the area of contact with soap and water as soon as possible.
    If the patient is also applying sunscreen to the application site, the patient should do so 30 minutes before or after the application of the gel.
    Patients should be advised that topical gels are typically flammable; therefore, fire, flame, and smoking should be avoided until the gel has dried.

    STORAGE

    Generic:
    - Store at room temperature (between 59 to 86 degrees F)
    Ditropan:
    - Store at controlled room temperature (between 68 and 77 degrees F)
    Ditropan XL:
    - Avoid excessive humidity
    - Protect from moisture
    - Store at 77 degrees F; excursions permitted to 59-86 degrees F
    Gelnique :
    - Avoid excessive humidity
    - Protect from moisture
    - Store at controlled room temperature (between 68 and 77 degrees F)
    Oxytrol:
    - Avoid excessive humidity
    - Do not store outside of the sealed pouch
    - Protect from moisture
    - Store at controlled room temperature (between 68 and 77 degrees F)
    - Store in original package until time of use
    Oxytrol for Women:
    - Avoid excessive humidity
    - Do not store outside of the sealed pouch
    - Protect from moisture
    - Store between 68 to 77 degrees F

    CONTRAINDICATIONS / PRECAUTIONS

    Angioedema

    All formulations of oxybutynin are contraindicated in patients with known hypersensitivity to oxybutynin; topical and transdermal formulations are also contraindicated in patients with known skin hypersensitivity to oxybutynin or other components of the products. Angioedema of the face, lips, tongue and/or larynx has been reported with oxybutynin (all routes). Airway obstruction, facial swelling, and anaphylactoid reactions requiring hospitalization and emergency medical treatment have occurred with initial and subsequent doses. Angioedema associated with upper airway swelling may be life-threatening. If involvement of the tongue, hypopharynx, or larynx occurs, oxybutynin should be promptly discontinued and appropriate therapy and/or measures necessary to ensure a patent airway should be promptly provided.

    Prostatic hypertrophy, urinary retention, urinary tract obstruction

    Due to its anticholinergic effects, oxybutynin is contraindicated in patients with urinary retention. Anticholinergics may precipitate urinary retention in patients with preexisting urinary tract obstruction or prostatic hypertrophy.

    Closed-angle glaucoma, contact lenses

    Oxybutynin is contraindicated in patients with uncontrolled narrow or closed-angle glaucoma. Oxybutynin may increase intraocular pressure and aqueous outflow resistance in patients with closed-angle glaucoma. The anticholinergic effects of oxybutynin may make the eyes dry, and this can cause irritation for wearers of contact lenses.

    Esophageal stricture, gastroesophageal reflux disease (GERD), gastroparesis, GI obstruction, hiatal hernia, ileus, pyloric stenosis, toxic megacolon, ulcerative colitis

    Because oxybutynin has a direct antispasmodic effect on smooth muscle that can delay gastric emptying, it is contraindicated for use in patients with gastric retention (e.g., gastroparesis, GI obstruction, pyloric stenosis). Oxybutynin is not recommended for use in the setting of decreased gastrointestinal motility , such as ileus, toxic megacolon, or severe ulcerative colitis; oxybutynin can precipitate a paralytic ileus. Oxybutynin should be used with caution in patients who have hiatal hernia and/or gastroesophageal reflux disease (GERD) because anticholinergics may aggravate these conditions. The extended-release formulation (e.g., Ditropan XL) should be used cautiously in patients with preexisting gastrointestinal narrowing; reports of obstructive symptoms in patients with known esophageal stricture in association with the ingestion of other drugs in nondeformable controlled-release formulations have been reported.

    Autonomic neuropathy, myasthenia gravis

    Avoid use of oxybutynin in patients with myasthenia gravis; the anticholinergic action of the drug may exacerbate clinical symptoms. If patients experience an exacerbation of myasthenia gravis, discontinue oxybutynin and promptly institute appropriate therapy. Patients with autonomic neuropathy may experience new or worsening symptoms, and may experience decreased gastrointestinal motility.

    Dementia

    The anticholinergic action of oxybutynin may exacerbate the clinical symptoms of patients with dementia. Therefore, oxybutynin should be used cautiously in this patient population. Close monitoring is advisable if treatment is necessary.

    Parkinson's disease

    Patients with Parkinson's disease may develop cognitive impairment or Parkinson's disease dementia (PDD) during the course of the disease. Although anticholinergic agents may be used to treat certain motor and non-motor symptoms of Parkinson's disease (e.g., tremor, urinary dysfunction), the anticholinergic effects of oxybutynin or similar drugs may exacerbate symptoms associated with cognitive impairment or PDD. Therefore, the use of anticholinergic agents should be discontinued or the dosages decreased, if possible, in Parkinson's patients with these conditions. Close monitoring is advisable if treatment with an anticholinergic agent is necessary.

    Hepatic disease

    Oxybutynin should be given with caution to patients who have hepatic disease due to lack of clinical data. Oxybutynin is extensively metabolized in the liver to both active and inactive metabolites.

    Anticholinergic medications, driving or operating machinery, ethanol ingestion

    Patients should use caution when driving or operating machinery until they know how oxybutynin affects them. A variety of central nervous system (CNS) anticholinergic effects have been reported with oxybutynin, including blurred vision, headache, dizziness, somnolence, confusion, and hallucinations; blurred vision, drowsiness, and dizziness may impair the ability to drive or perform other hazardous tasks. Patients should be monitored for signs of anticholinergic CNS effects, particularly after beginning treatment. If a patient experiences anticholinergic CNS effects, drug discontinuation should be considered. Ethanol ingestion can magnify sedative effects and is best avoided; interactions have been reported where the combination has increased the risk for CNS effects such as drowsiness. The clinician may also need to consider the effects of other anticholinergic medications, since additive CNS effects may occur.

    Ambient temperature increase

    Heat prostration due to decreased sweating may occur due to the anticholinergic properties of oxybutynin. Heat prostration can occur when anticholinergic medicines are administered in the presence of high environmental temperature (ambient temperature increase). Patients should use caution in environmental exposure.

    Accidental exposure, tobacco smoking

    Proper use of oxybutynin topical gels is essential to ensure safety. Oxybutynin topical gels are typically flammable, therefore exposure to fire, flame, and tobacco smoking should be avoided until the gel has dried. Accidental exposure of another person to oxybutynin topical gels can occur when vigorous skin-to-skin contact is made with the application site. To minimize the potential transfer of the drug from the treated skin to that of another person, patients should cover the application site with clothing after the gel has dried if direct skin-to-skin contact at the application site is anticipated.

    Pregnancy

    There are no adequate and well-controlled studies of topical or oral oxybutynin use in human pregnancy. Subcutaneous administration to rats at doses up to 25 mg/kg (approximately 50 times the human exposure based on surface area) and to rabbits at doses up to 0.4 mg/kg (approximately 1 times the human exposure) revealed no evidence of harm to the fetus due to oxybutynin. Reproduction studies with oxybutynin in the mouse, rat, hamster, and rabbit showed no evidence of impaired fertility. Oxybutynin should not be given to pregnant women unless, in the judgment of the physician, the probable clinical benefits outweigh the possible risks.

    Breast-feeding

    It is not known if oxybutynin is excreted in breast milk. Because many drugs are excreted in human milk, caution should be exercised when oxybutynin is administered to a nursing woman. Because an infant is usually very sensitive to anticholinergic effects of drugs, there may be a risk for adverse effects if the infant is exposed to oxybutynin via breast-feeding. Lactation suppression has been reported during postmarketing use of immediate-release oxybutynin. 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 administered drug, healthcare providers are encouraged to report the adverse effect to the FDA.

    Geriatric

    When needed, oral oxybutynin should be used cautiously in geriatric patients. Clinical trials have reported that overall, anticholinergic side effects of oxybutynin are similar in young adults and in those over the age of 65 years. However, some elderly adults may be more susceptible to anticholinergic side effects of the drug. According to the Beers Criteria, antimuscarinics with strong anticholinergic properties, such as oxybutynin, are considered potentially inappropriate medications (PIMs) in geriatric patients with dementia/cognitive impairment (adverse CNS effects) or delirium/high risk of delirium (possible new-onset or worsening delirium), and it is recommended that use in these patient populations be avoided. The federal Omnibus Budget Reconciliation Act (OBRA) regulates medication use in residents of long-term care facilities (LTCFs). According to the OBRA guidelines, assessment of the underlying causes and identification of the type/category of urinary incontinence needs to be documented prior to or soon after initiating treatment with a medication to manage urinary incontinence. These medications have specific and limited indications based on the cause and categorization of incontinence. Patients should be assessed periodically for medication effects on urinary incontinence as well as lower urinary tract symptoms and treatment tolerability. Anticholinergic medications, such as oxybutynin, may cause mental status changes, constipation, drowsiness, dizziness, dryness of mucus membranes, blurred vision, urinary retention, or other adverse effects that can be problematic in the elderly.

    Infants

    Oxybutynin should be used with caution in young children, who may be more susceptible to adverse anticholinergic effects than older children or adults; however, weight-based dosing has been used in very young children. Oxybutynin immediate-release products are approved for use in children over 5 years of age with overactivity of the bladder detrusor muscle due to various conditions ; however, do not use the extended-release product in pediatric patients who cannot swallow the tablet whole. Transdermal oxybutynin continues to be evaluated for safety and efficacy in pediatric patients; pediatric patients should receive oxybutynin under the supervision of a prescriber; children should not use the non-prescription product. No oxybutynin product is approved for use in infants.

    ADVERSE REACTIONS

    Severe

    bronchospasm / Rapid / 1.0-4.9
    keratoconjunctivitis / Early / 1.0-4.9
    anaphylactoid reactions / Rapid / Incidence not known
    angioedema / Rapid / Incidence not known
    seizures / Delayed / Incidence not known
    arrhythmia exacerbation / Early / Incidence not known
    ocular hypertension / Delayed / Incidence not known
    visual impairment / Early / Incidence not known

    Moderate

    constipation / Delayed / 1.3-15.1
    blurred vision / Early / 1.0-9.6
    erythema / Early / 3.7-8.3
    urinary retention / Early / 1.2-6.0
    dysphagia / Delayed / 1.0-4.9
    confusion / Early / 1.0-4.9
    flank pain / Delayed / 1.0-4.9
    cystitis / Delayed / 1.0-4.9
    dysuria / Early / 1.0-4.9
    palpitations / Early / 1.0-4.9
    peripheral edema / Delayed / 1.0-4.9
    edema / Delayed / 1.0-4.9
    sinus tachycardia / Rapid / 1.0-4.9
    fluid retention / Delayed / 1.0-4.9
    hyperglycemia / Delayed / 1.0-4.9
    contact dermatitis / Delayed / 1.8-1.8
    dysphonia / Delayed / 0-1.0
    anhidrosis / Delayed / Incidence not known
    delirium / Early / Incidence not known
    memory impairment / Delayed / Incidence not known
    hallucinations / Early / Incidence not known
    psychosis / Early / Incidence not known
    impotence (erectile dysfunction) / Delayed / Incidence not known
    hypertension / Early / Incidence not known
    QT prolongation / Rapid / Incidence not known
    chest pain (unspecified) / Early / Incidence not known
    cycloplegia / Early / Incidence not known
    lactation suppression / Early / Incidence not known

    Mild

    xerostomia / Early / 4.1-71.4
    dizziness / Early / 2.8-16.6
    drowsiness / Early / 5.6-14.0
    nausea / Early / 4.5-11.6
    diarrhea / Early / 1.0-7.9
    headache / Early / 1.5-7.5
    skin irritation / Early / 1.0-6.4
    dyspepsia / Early / 4.5-6.0
    insomnia / Early / 3.0-5.5
    infection / Delayed / 1.0-5.4
    vomiting / Early / 1.0-4.9
    abdominal pain / Early / 1.0-4.9
    eructation / Early / 1.0-4.9
    flatulence / Early / 1.0-4.9
    urticaria / Rapid / 1.0-4.9
    pruritus / Rapid / 1.0-4.9
    xerosis / Delayed / 1.0-4.9
    cough / Delayed / 1.0-4.9
    hoarseness / Early / 1.0-4.9
    nasal dryness / Early / 1.0-4.9
    pharyngitis / Delayed / 1.0-4.9
    nasal congestion / Early / 1.0-4.9
    flushing / Rapid / 1.0-4.9
    dysgeusia / Early / 1.0-4.9
    fatigue / Early / 1.0-4.9
    asthenia / Delayed / 1.0-4.9
    back pain / Delayed / 1.0-4.9
    arthralgia / Delayed / 1.0-4.9
    increased urinary frequency / Early / 1.0-4.9
    ocular irritation / Rapid / 1.0-4.9
    rash (unspecified) / Early / 3.3-3.3
    vesicular rash / Delayed / 3.2-3.2
    xerophthalmia / Early / 1.0-3.1
    maculopapular rash / Early / 2.5-2.5
    anorexia / Delayed / 0-1.0
    gastroesophageal reflux / Delayed / 1.0-1.0
    polydipsia / Early / 0-1.0
    fever / Early / Incidence not known
    rhinitis / Early / Incidence not known
    agitation / Early / Incidence not known
    mydriasis / Early / Incidence not known
    ocular pain / Early / Incidence not known

    DRUG INTERACTIONS

    Acetaminophen; Aspirin, ASA; Caffeine: (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms, increase urine output, and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. Patients may wish to limit their intake of caffeinated drugs, dietary supplements (e.g., guarana), or beverages (e.g., green tea, other teas, coffee, colas).
    Acetaminophen; Butalbital: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Acetaminophen; Butalbital; Caffeine: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy. (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms, increase urine output, and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. Patients may wish to limit their intake of caffeinated drugs, dietary supplements (e.g., guarana), or beverages (e.g., green tea, other teas, coffee, colas).
    Acetaminophen; Butalbital; Caffeine; Codeine: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy. (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. (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms, increase urine output, and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. Patients may wish to limit their intake of caffeinated drugs, dietary supplements (e.g., guarana), or beverages (e.g., green tea, other teas, coffee, colas).
    Acetaminophen; Caffeine; 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. (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms, increase urine output, and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. Patients may wish to limit their intake of caffeinated drugs, dietary supplements (e.g., guarana), or beverages (e.g., green tea, other teas, coffee, colas).
    Acetaminophen; Caffeine; Magnesium Salicylate; 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. (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms, increase urine output, and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. Patients may wish to limit their intake of caffeinated drugs, dietary supplements (e.g., guarana), or beverages (e.g., green tea, other teas, coffee, colas).
    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. (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms, increase urine output, and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. Patients may wish to limit their intake of caffeinated drugs, dietary supplements (e.g., guarana), or beverages (e.g., green tea, other teas, coffee, colas).
    Acetaminophen; Chlorpheniramine; Dextromethorphan; 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.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; 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.
    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: (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; 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.
    Acetaminophen; Dichloralphenazone; Isometheptene: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    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: (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.
    Acetaminophen; 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.
    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.
    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.
    Alprazolam: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Aluminum Hydroxide: (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: (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: (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: (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: (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: (Moderate) Additive anticholinergic effects may be seen when oxybutynin is used concomitantly with drugs with moderate to significant anticholinergic effects such as amantadine. Clinicians should note that anticholinergic effects might be seen not only on bladder smooth muscle, but also on GI function, the eye, and temperature regulation. With many of the listed agents, additive drowsiness may also occur when combined with oxybutynin.
    Ambenonium Chloride: (Moderate) Oxybutynin is an antimuscarinic; the muscarinic actions of ambenonium chloride could be antagonized when used concomitantly with oxybutynin.
    Amitriptyline; Chlordiazepoxide: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Amobarbital: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Amoxapine: (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.
    Amoxicillin; Clarithromycin; Lansoprazole: (Moderate) Oxybutynin is metabolized by CYP3A4. Serum concentrations of oxybutynin may be increased when administered with inhibitors of the CYP3A4 enzyme system, including clarithromycin.
    Amoxicillin; Clarithromycin; Omeprazole: (Moderate) Oxybutynin is metabolized by CYP3A4. Serum concentrations of oxybutynin may be increased when administered with inhibitors of the CYP3A4 enzyme system, including clarithromycin.
    Amprenavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Antacids: (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.
    Antidiarrheals: (Moderate) Both antidiarrheals and anticholinergics, such as oxybutynin, decrease GI motility. Use of these drugs together may produce additive effects on the GI track; thereby increasing the risk for toxic megacolon.
    Anxiolytics; Sedatives; and Hypnotics: (Moderate) Oxybutynin causes CNS-depressant effects including somnolence and drowsiness; concurrent use with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics, can increase the total sedative effects of oxybutynin.
    Aprepitant, Fosaprepitant: (Moderate) Use caution if oxybutynin and aprepitant, fosaprepitant are used concurrently and monitor for an increase in oxybutynin-related adverse effects for several days after administration of a multi-day aprepitant regimen. Oxybutynin is a CYP3A4 substrate. Aprepitant, when administered as a 3-day oral regimen (125 mg/80 mg/80 mg), is a moderate CYP3A4 inhibitor and inducer and may increase plasma concentrations of oxybutynin. For example, a 5-day oral aprepitant regimen increased the AUC of another CYP3A4 substrate, midazolam (single dose), by 2.3-fold on day 1 and by 3.3-fold on day 5. After a 3-day oral aprepitant regimen, the AUC of midazolam (given on days 1, 4, 8, and 15) increased by 25% on day 4, and then decreased by 19% and 4% on days 8 and 15, respectively. As a single 125 mg or 40 mg oral dose, the inhibitory effect of aprepitant on CYP3A4 is weak, with the AUC of midazolam increased by 1.5-fold and 1.2-fold, respectively. After administration, fosaprepitant is rapidly converted to aprepitant and shares many of the same drug interactions. However, as a single 150 mg intravenous dose, fosaprepitant only weakly inhibits CYP3A4 for a duration of 2 days; there is no evidence of CYP3A4 induction. Fosaprepitant 150 mg IV as a single dose increased the AUC of midazolam (given on days 1 and 4) by approximately 1.8-fold on day 1; there was no effect on day 4. Less than a 2-fold increase in the midazolam AUC is not considered clinically important.
    Aspirin, ASA; Butalbital; Caffeine: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy. (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms, increase urine output, and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. Patients may wish to limit their intake of caffeinated drugs, dietary supplements (e.g., guarana), or beverages (e.g., green tea, other teas, coffee, colas).
    Aspirin, ASA; Butalbital; Caffeine; Codeine: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy. (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. (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms, increase urine output, and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. Patients may wish to limit their intake of caffeinated drugs, dietary supplements (e.g., guarana), or beverages (e.g., green tea, other teas, coffee, colas).
    Aspirin, ASA; Caffeine; 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. (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms, increase urine output, and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. Patients may wish to limit their intake of caffeinated drugs, dietary supplements (e.g., guarana), or beverages (e.g., green tea, other teas, coffee, colas).
    Aspirin, ASA; Carisoprodol; 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.
    Aspirin, ASA; Oxycodone: (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.
    Atazanavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Atazanavir; Cobicistat: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together. (Moderate) The plasma concentrations of oxybutynin may be elevated when administered concurrently with cobicistat. Clinical monitoring for adverse effects, such as increased anticholinergic activity, is recommended during coadministration. Cobicistat is a CYP3A4 inhibitor, while oxybutynin is a CYP3A4 substrate.
    Atropine; Edrophonium: (Moderate) Oxybutynin is an antimuscarinic; the muscarinic actions of edrophonium chloride could be antagonized when used concomitantly with oxybutynin.
    Atropine; Hyoscyamine; Phenobarbital; Scopolamine: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Barbiturates: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Belladonna Alkaloids; Ergotamine; Phenobarbital: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    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.
    Benzodiazepines: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Bismuth Subsalicylate: (Moderate) Both antidiarrheals and anticholinergics, such as oxybutynin, decrease GI motility. Use of these drugs together may produce additive effects on the GI track; thereby increasing the risk for toxic megacolon.
    Bismuth Subsalicylate; Metronidazole; Tetracycline: (Moderate) Both antidiarrheals and anticholinergics, such as oxybutynin, decrease GI motility. Use of these drugs together may produce additive effects on the GI track; thereby increasing the risk for toxic megacolon.
    Boceprevir: (Moderate) Close clinical monitoring is advised when administering oxybutynin with boceprevir due to an increased potential for oxybutynin-related adverse events. If oxybutynin dose adjustments are made, re-adjust the dose upon completion of boceprevir treatment. Although this interaction has not been studied, predictions about the interaction can be made based on the metabolic pathway of oxybutynin. Oxybutynin is partially metabolized by the hepatic isoenzyme CYP3A4; boceprevir inhibits this isoenzyme. Coadministration may result in elevated oxybutynin plasma concentrations.
    Bosentan: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as bosentan, may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    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).
    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: (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.
    Buprenorphine: (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: (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: (Moderate) Additive anticholinergic effects may be seen when oxybutynin is used concomitantly with other drugs with moderate to significant anticholinergic effects including bupropion. Clinicians should note that anticholinergic effects might be seen not only on bladder smooth muscle, but also on GI function, the eye, and temperature regulation. Additive drowsiness may also occur.
    Bupropion; Naltrexone: (Moderate) Additive anticholinergic effects may be seen when oxybutynin is used concomitantly with other drugs with moderate to significant anticholinergic effects including bupropion. Clinicians should note that anticholinergic effects might be seen not only on bladder smooth muscle, but also on GI function, the eye, and temperature regulation. Additive drowsiness may also occur.
    Buspirone: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Butabarbital: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    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.
    Caffeine: (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms, increase urine output, and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. Patients may wish to limit their intake of caffeinated drugs, dietary supplements (e.g., guarana), or beverages (e.g., green tea, other teas, coffee, colas).
    Caffeine; Ergotamine: (Minor) Consuming greater than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms, increase urine output, and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin. Patients may wish to limit their intake of caffeinated drugs, dietary supplements (e.g., guarana), or beverages (e.g., green tea, other teas, coffee, colas).
    Calcium Carbonate: (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.
    Calcium Carbonate; Magnesium Hydroxide: (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.
    Calcium Carbonate; Risedronate: (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.
    Calcium; Vitamin D: (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.
    Carbamazepine: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as carbamazepine, may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    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 central antimuscarinic actions, anticholinergics can potentiate the dopaminergic effects of levodopa. Antimuscarinics, by slowing GI transit, may also decrease levodopa bioavailability; however, this mechanism appears to be of modest clinical significance. Antimuscarinic agents targeted specifically for urinary incontinence may be less likely to produce pronounced effects on levodopa response than those with more pronounced systemic action.
    Carbidopa; Levodopa; Entacapone: (Minor) Through central antimuscarinic actions, anticholinergics can potentiate the dopaminergic effects of levodopa. Antimuscarinics, by slowing GI transit, may also decrease levodopa bioavailability; however, this mechanism appears to be of modest clinical significance. Antimuscarinic agents targeted specifically for urinary incontinence may be less likely to produce pronounced effects on levodopa response than those with more pronounced systemic action.
    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: (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.
    Ceritinib: (Moderate) Monitor for oxybutynin-related adverse reactions if coadministration with ceritinib is necessary. Ceritinib is a CYP3A4 inhibitor and oxybutynin is metabolized by CYP3A4. Coadministration with a strong CYP3A4 inhibitor increased oxybutynin exposure by approximately 2-fold; other CYP3A4 inhibitors may have a similar effect. The clinical relevance of this potential interaction is unknown.
    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.
    Chloral Hydrate: (Moderate) Oxybutynin causes CNS-depressant effects including somnolence and drowsiness; concurrent use with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics, can increase the total sedative effects of oxybutynin.
    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.
    Chlordiazepoxide: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Chlordiazepoxide; Clidinium: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    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: (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: (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: (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: (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: (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.
    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.
    Cisapride: (Moderate) Oxybutynin is an antimuscarinic that decreases GI motility; drugs that exert antimuscarinic properties may pharmacodynamically oppose the effects of prokinetic agents such as cisapride. The clinical significance of this interaction is unknown.
    Clarithromycin: (Moderate) Oxybutynin is metabolized by CYP3A4. Serum concentrations of oxybutynin may be increased when administered with inhibitors of the CYP3A4 enzyme system, including clarithromycin.
    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.
    Clonazepam: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Clorazepate: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Clozapine: (Moderate) Additive anticholinergic effects may be seen when oxybutynin is used concomitantly with other commonly used drugs with moderate to significant anticholinergic effects including clozapine. Clinicians should note that anticholinergic effects might be seen not only on bladder smooth muscle, but also on GI function, the eye, and temperature regulation. Additive drowsiness may also occur.
    Cobicistat: (Moderate) The plasma concentrations of oxybutynin may be elevated when administered concurrently with cobicistat. Clinical monitoring for adverse effects, such as increased anticholinergic activity, is recommended during coadministration. Cobicistat is a CYP3A4 inhibitor, while oxybutynin is a CYP3A4 substrate.
    Cobicistat; Elvitegravir; Emtricitabine; Tenofovir Alafenamide: (Moderate) The plasma concentrations of oxybutynin may be elevated when administered concurrently with cobicistat. Clinical monitoring for adverse effects, such as increased anticholinergic activity, is recommended during coadministration. Cobicistat is a CYP3A4 inhibitor, while oxybutynin is a CYP3A4 substrate.
    Cobicistat; Elvitegravir; Emtricitabine; Tenofovir Disoproxil Fumarate: (Moderate) The plasma concentrations of oxybutynin may be elevated when administered concurrently with cobicistat. Clinical monitoring for adverse effects, such as increased anticholinergic activity, is recommended during coadministration. Cobicistat is a CYP3A4 inhibitor, while oxybutynin is a CYP3A4 substrate.
    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: (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: (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: (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.
    Crizotinib: (Minor) Monitor for oxybutynin-related adverse reactions if coadministration with crizotinib is necessary. Oxybutynin is a CYP3A4 substrate and crizotinib is a moderate CYP3A4 inhibitor. Concomitant use with moderate CYP3A4 inhibitors may alter the mean pharmacokinetic parameters of oxybutynin, although the clinical relevance of these potential interactions is unknown. The manufacturer of oxybutynin recommends administering with caution.
    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.
    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.
    Dalfopristin; Quinupristin: (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme, such as streptogramins, may increase the serum concentrations of oxybutynin. The manufacturer recommends caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Danazol: (Moderate) Oxybutynin is metabolized by CYP3A4. Serum concentrations of oxybutynin may be increased if coadministered with inhibitors of CYP3A4 including danazol. The manufacturer recommends that caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Darunavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Darunavir; Cobicistat: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together. (Moderate) The plasma concentrations of oxybutynin may be elevated when administered concurrently with cobicistat. Clinical monitoring for adverse effects, such as increased anticholinergic activity, is recommended during coadministration. Cobicistat is a CYP3A4 inhibitor, while oxybutynin is a CYP3A4 substrate.
    Dasabuvir; Ombitasvir; Paritaprevir; Ritonavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Delavirdine: (Moderate) Oxybutynin is metabolized by CYP3A4. Serum concentrations of oxybutynin may be increased if coadministered with inhibitors of CYP3A4 including delavirdine. The manufacturer recommends that caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Desmopressin: (Major) Hyponatremia-induced convulsions have been rarely reported when oxybutynin and desmopressin are used concomitantly. Use these drugs together with caution, and monitor patients for signs and symptoms of hyponatremia.
    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: (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; 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.
    Dextromethorphan; Promethazine: (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: (Moderate) The anticholinergic effects of quinidine may be significant and may be enhanced when combined with antimuscarinics.
    Diazepam: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    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: (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.
    Diltiazem: (Moderate) Oxybutynin is metabolized by CYP3A4. Serum concentrations of oxybutynin may be increased if coadministered with inhibitors of CYP3A4 including diltiazem. The manufacturer recommends that caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    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: (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: (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.
    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.
    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.
    Dronedarone: (Moderate) Dronedarone is metabolized by and is an inhibitor of CYP3A. Oxybutynin is a substrate for CYP3A4. The concomitant administration of dronedarone and CYP3A substrates may result in increased exposure of the substrate and should, therefore, be undertaken with caution.
    Edrophonium: (Moderate) Oxybutynin is an antimuscarinic; the muscarinic actions of edrophonium chloride could be antagonized when used concomitantly with oxybutynin.
    Efavirenz: (Moderate) Oxybutynin is metabolized by CYP3A4. Drugs that induce CYP3A4, such as efavirenz, may cause decreased serum concentrations of oxybutynin. The clinical significance of such interactions is not known; however patients receiving oxybutynin with efavirenz or efavirenz-containing products (e.g. efavirenz; emtricitabine; tenofovir) concomitantly should be monitored for efficacy.
    Efavirenz; Emtricitabine; Tenofovir: (Moderate) Oxybutynin is metabolized by CYP3A4. Drugs that induce CYP3A4, such as efavirenz, may cause decreased serum concentrations of oxybutynin. The clinical significance of such interactions is not known; however patients receiving oxybutynin with efavirenz or efavirenz-containing products (e.g. efavirenz; emtricitabine; tenofovir) concomitantly should be monitored for efficacy.
    Elbasvir; Grazoprevir: (Moderate) Administering oxybutynin with elbasvir; grazoprevir may result in elevated oxybutynin plasma concentrations. Oxybutynin is a substrate of CYP3A; grazoprevir is a weak CYP3A inhibitor. If these drugs are used together, closely monitor for signs of adverse events.
    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.
    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: (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.
    Estazolam: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Eszopiclone: (Moderate) Oxybutynin causes CNS-depressant effects including somnolence and drowsiness; concurrent use with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics, can increase the total sedative effects of oxybutynin.
    Ethanol: (Moderate) Alcohol may aggravate bladder symptoms and counteract the effectiveness of oxybutynin to some degree. In addition, ethanol is a CNS-depressant and may cause additive sedative effects when used concomitantly with oxybutynin.
    Ethotoin: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as hydantoin anticonvulsants, may reduce the effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    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.
    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.
    Fluconazole: (Moderate) Oxybutynin is metabolized by CYP3A4. Serum concentrations of oxybutynin may be increased if coadministered with inhibitors of CYP3A4 including fluconazole. The manufacturer recommends that caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Fluoxetine: (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme, such as fluoxetine, may increase the serum concentrations of oxybutynin. The manufacturer recommends caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Fluoxetine; Olanzapine: (Moderate) Additive anticholinergic effects may be seen when oxybutynin is used concomitantly with other drugs that have moderate to significant anticholinergic effects, including olanzapine. Clinicians should note that anticholinergic effects might be seen not only on bladder smooth muscle, but also on GI function, the eye, and temperature regulation. Additive drowsiness may also occur. (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme, such as fluoxetine, may increase the serum concentrations of oxybutynin. The manufacturer recommends caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    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.
    Flurazepam: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    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.
    Fluvoxamine: (Moderate) Oxybutynin is metabolized by CYP3A4. Serum concentrations of oxybutynin may be increased if coadministered with inhibitors of CYP3A4 including fluvoxamine. The manufacturer recommends that caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Fosamprenavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Fosphenytoin: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as hydantoin anticonvulsants, may reduce the effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    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.
    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.
    Grapefruit juice: (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme system, such as grapefruit juice, may alter oxybutynin mean pharmacokinetic parameters. The clinical significance of such interactions is not known; however, the manufacturer recommends that caution be used when oxybutynin is co-administered with CYP3A4 inhibitors.
    Green Tea: (Minor) Some green tea products contain caffeine. Consuming more than 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms and counteract the effectiveness of drugs used to treat overactive bladder such as oxybutynin.
    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.
    Guarana: (Minor) Caffeine is an active constituent of guarana. Consuming > 400 mg/day caffeine has been associated with the development of urinary incontinence. Caffeine may aggravate bladder symptoms and counteract the effectiveness of drugs used to treat overactive bladder (i.e., darifenacin, oxybutynin, trospium, or tolterodine) to some degree. Patients with overactive bladder may wish to limit their intake of caffeinated drugs, dietary supplements (i.e., guarana), beverages (i.e., teas, coffee, colas), or foods (i.e., chocolate).
    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.
    Hydantoins: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as hydantoin anticonvulsants, may reduce the effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    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: (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.
    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.
    Hydroquinone: (Moderate) The effect on the pharmacokinetics of oxybutynin topical gel when sunscreens were applied 30 minutes before or after oxybutynin gel was evaluated in a single-dose randomized crossover study (n=16). The study revealed no difference in the absorption of oxybutynin gel when applied in this manner. However, the effects of sunscreen on oxybutynin absorption when used within 30 minutes of gel application have not been studied. Therefore, the manufacturer recommends that patients use sunscreen either 30 minutes before or after gel application.
    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; Oxycodone: (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.
    Idelalisib: (Major) Avoid concomitant use of idelalisib, a strong CYP3A inhibitor, with oxybutynin, a CYP3A substrate, as oxybutynin toxicities may be significantly increased. The AUC of a sensitive CYP3A substrate was increased 5.4-fold when coadministered with idelalisib.
    Imatinib: (Moderate) Oxybutynin is metabolized by CYP3A4. Serum concentrations of oxybutynin may be increased if coadministered with inhibitors of CYP3A4 including imatinib. The manufacturer recommends that caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Indinavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    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.
    Isavuconazonium: (Moderate) Concomitant use of isavuconazonium with oxybutynin may result in increased serum concentrations of oxybutynin. Oxybutynin is a substrate of the hepatic isoenzyme CYP3A4; isavuconazole, the active moiety of isavuconazonium, is a moderate inhibitor of this enzyme. Caution and close monitoring are advised if these drugs are used together.
    Isoniazid, INH; Pyrazinamide, PZA; Rifampin: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as rifamycins, may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Isoniazid, INH; Rifampin: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as rifamycins, may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    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. In addition, oxybutynin is metabolized by CYP3A4. Anticholinergic side effects may be increased when oxybutynin is used in combination with itraconazole. In healthy subjects receiving both itraconazole and oxybutynin, serum concentrations of oxybutynin were doubled; however, the serum concentrations of the active metabolite, N-desethoxybutynin, were not significantly changed. Since the pharmacologic effects of oxybutynin are mainly due to the active metabolite, adverse reactions associated with this interaction should be minimal.
    Ivacaftor: (Moderate) Use caution when administering ivacaftor and oxybutynin concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as oxybutynin, can increase oxybutynin exposure leading to increased or prolonged therapeutic effects and adverse events.
    Ketoconazole: (Moderate) Systemic azole antifungals, such as ketoconazole, are CYP3A4 inhibitors and can reduce the metabolism of drugs metabolized by CYP3A4, including oxybutynin. Serum concentrations of oxybutynin were approximately 2-fold higher when administered with ketoconazole or itraconazole. Oxybutynin should be used cautiously in patients receiving these drugs. In addition, antimuscarinic drugs can raise intragastric pH. This effect may decrease the oral bioavailability of ketoconazole.
    Lesinurad: (Moderate) Lesinurad may decrease the systemic exposure and therapeutic efficacy of oxybutynin; monitor for potential reduction in efficacy. Oxybutynin is a CYP3A substrate, and lesinurad is a weak CYP3A inducer.
    Lesinurad; Allopurinol: (Moderate) Lesinurad may decrease the systemic exposure and therapeutic efficacy of oxybutynin; monitor for potential reduction in efficacy. Oxybutynin is a CYP3A substrate, and lesinurad is a weak CYP3A inducer.
    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 central antimuscarinic actions, anticholinergics can potentiate the dopaminergic effects of levodopa. Antimuscarinics, by slowing GI transit, may also decrease levodopa bioavailability; however, this mechanism appears to be of modest clinical significance. Antimuscarinic agents targeted specifically for urinary incontinence may be less likely to produce pronounced effects on levodopa response than those with more pronounced systemic action.
    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.
    Loop diuretics: (Minor) Diuretics can increase urinary frequency, which may aggravate bladder symptoms.
    Loperamide: (Moderate) Both antidiarrheals and anticholinergics, such as oxybutynin, decrease GI motility. Use of these drugs together may produce additive effects on the GI track; thereby increasing the risk for toxic megacolon.
    Loperamide; Simethicone: (Moderate) Both antidiarrheals and anticholinergics, such as oxybutynin, decrease GI motility. Use of these drugs together may produce additive effects on the GI track; thereby increasing the risk for toxic megacolon.
    Lopinavir; Ritonavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Lorazepam: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    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.
    Luliconazole: (Moderate) Theoretically, luliconazole may increase the side effects of oxybutynin, which is a CYP (2C19 or 3A4) substrate. Monitor patients for adverse effects of oxybutynin, such as CNS and anticholinergic effects. In vitro, therapeutic doses of luliconazole inhibit the activity of CYP (2C19 or 3A4) and small systemic concentrations may be noted with topical application, particularly when applied to patients with moderate to severe tinea cruris. No in vivo drug interaction trials were conducted prior to the approval of luliconazole.
    Lumacaftor; Ivacaftor: (Minor) Lumacaftor; ivacaftor may reduce the efficacy of oxybutynin by decreasing its systemic exposure; if used together, monitor patients for anticholinergic efficacy. Oxybutynin is a substrate of CYP3A4, and lumacaftor is a strong CYP3A inducer.
    Lumacaftor; Ivacaftor: (Moderate) Use caution when administering ivacaftor and oxybutynin concurrently. Ivacaftor is an inhibitor of CYP3A. Co-administration of ivacaftor with CYP3A substrates, such as oxybutynin, can increase oxybutynin exposure leading to increased or prolonged therapeutic effects and adverse events.
    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: (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.
    Maprotiline: (Moderate) Additive anticholinergic effects may be seen when oxybutynin is used concomitantly with other commonly used drugs with moderate to significant anticholinergic effects including maprotiline. Clinicians should note that anticholinergic effects might be seen not only on bladder smooth muscle, but also on GI function, the eye, and temperature regulation. Additive drowsiness may also occur.
    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.
    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: (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: (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.
    Mephobarbital: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Meprobamate: (Moderate) Oxybutynin causes CNS-depressant effects including somnolence and drowsiness; concurrent use with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics, can increase the total sedative effects of oxybutynin.
    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.
    Methohexital: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Metoclopramide: (Moderate) Drugs with significant antimuscarinic activity, such as anticholinergics and antimuscarinics, may slow GI motility and thus may reduce the prokinetic actions of metoclopramide. Monitor patients for an increase in gastrointestinal complaints, such as reflux or constipation. Additive drowsiness may occur as well. The clinical significance is uncertain.
    Midazolam: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Mifepristone, RU-486: (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme, such as mifepristone, may increase the serum concentrations of oxybutynin. The manufacturer recommends caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Mirabegron: (Moderate) Mirabegron should be administered with caution in patients taking antimuscarinic medications for the treatment of overactive bladder, such as oxybutynin, because of the risk of urinary retention.
    Mirtazapine: (Moderate) Mirtazapine exhibits weak anticholinergic activity that is not expected to be clinically significant. However, the anticholinergic effects may be additive to the antimuscarinics. 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.
    Mitotane: (Moderate) Mitotane is a strong CYP3A4 inducer and oxybutynin is a CYP3A4 substrate. Coadministration may result in decreased plasma concentrations of oxybutynin. If these drugs are used together, monitor patients for decreased oxybutynin efficacy; oxybutynin dosage adjustments may be needed.
    Molindone: (Moderate) Antipsychotics are associated with anticholinergic effects; therefore, additive effects may be seen during concurrent use of molindone and other drugs having anticholinergic activity such as antimuscarinics. 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 CNS effects may also occur.
    Morphine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when morphine is used concomitantly with an anticholinergic drug. The concomitant use of morphine 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.
    Morphine; Naltrexone: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when morphine is used concomitantly with an anticholinergic drug. The concomitant use of morphine 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.
    Nabilone: (Moderate) Concurrent use of nabilone with anticholinergics may result in pronounced tachycardia and drowsiness.
    Nalbuphine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when nalbuphine is used concomitantly with an anticholinergic drug. The concomitant use of nalbuphine 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.
    Nefazodone: (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme, such as nefazodone, may increase the serum concentrations of oxybutynin. The manufacturer recommends caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Nelfinavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Neostigmine: (Moderate) Oxybutynin is an antimuscarinic; the muscarinic actions of neostigmine could be antagonized when used concomitantly with oxybutynin.
    Nitrofurantoin: (Moderate) Antimuscarinics can delay gastric emptying, possibly increasing the bioavailability of nitrofurantoin.
    Olanzapine: (Moderate) Additive anticholinergic effects may be seen when oxybutynin is used concomitantly with other drugs that have moderate to significant anticholinergic effects, including olanzapine. Clinicians should note that anticholinergic effects might be seen not only on bladder smooth muscle, but also on GI function, the eye, and temperature regulation. Additive drowsiness may also occur.
    Ombitasvir; Paritaprevir; Ritonavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Omeprazole; Sodium Bicarbonate: (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.
    Ondansetron: (Moderate) The plasma concentrations of oxybutynin may be elevated when administered concurrently with cobicistat. Clinical monitoring for adverse effects, such as increased anticholinergic activity, is recommended during coadministration. Cobicistat is a CYP3A4 inhibitor, while oxybutynin is a CYP3A4 substrate.
    Oritavancin: (Minor) Oxybutynin is metabolized by CYP3A4; oritavancin is a weak CYP3A4 inducer. Plasma concentrations and efficacy of oxybutynin may be reduced if these drugs are administered concurrently.
    Orphenadrine: (Moderate) Additive anticholinergic effects may be seen when oxybutynin is used concomitantly with other drugs that have moderate to significant anticholinergic effects, including orphenadrine. Clinicians should note that anticholinergic effects might be seen not only on bladder smooth muscle, but also on GI function, the eye, and temperature regulation. Additive drowsiness may also occur.
    Oxazepam: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Oxycodone: (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.
    Oxymorphone: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when oxymorphone is used concomitantly with an anticholinergic drug. The concomitant use of oxymorphone 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.
    Pazopanib: (Moderate) Pazopanib is a weak inhibitor of CYP3A4. Coadministration of pazopanib and oxybutynin a CYP3A4 substrate, may cause an increase in systemic concentrations of oxybutynin. Use caution when administering these drugs concomitantly.
    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.
    Pentazocine; Naloxone: (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.
    Pentobarbital: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Perphenazine: (Moderate) Additive anticholinergic effects may be seen when anticholinergics are used concomitantly with phenothiazines, including perphenazine. 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.
    Perphenazine; Amitriptyline: (Moderate) Additive anticholinergic effects may be seen when anticholinergics are used concomitantly with phenothiazines, including perphenazine. 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.
    Phenobarbital: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Phentermine; Topiramate: (Moderate) Use caution if carbonic anhydrase inhibitors are administered with anticholinergics and monitor for excessive anticholinergic adverse effects. The use of topiramate with agents that may increase the risk for heat-related disorders, such as anticholinergics, may lead to oligohidrosis, hyperthermia and/or heat stroke.
    Phenylephrine; Promethazine: (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.
    Phenytoin: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as hydantoin anticonvulsants, may reduce the effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Physostigmine: (Moderate) Oxybutynin is an antimuscarinic; the muscarinic actions of physostigmine could be antagonized when used concomitantly with oxybutynin.
    Posaconazole: (Moderate) Posaconazole and oxybutynin should be coadministered with caution due to an increased potential for oxybutynin-related adverse events. Posaconazole is a potent inhibitor of CYP3A4, an isoenzyme responsible for the metabolism of oxybutynin. These drugs used in combination may result in elevated oxybutynin plasma concentrations, causing an increased risk for oxybutynin-related adverse events.
    Potassium: (Major) Drugs that decrease GI motility may increase the risk of GI irritation from sustained-release solid oral dosage forms of potassium salts. The use of solid oral dosage forms of potassium chloride is contraindicated in patients taking glycopyrrolate oral solution. In one study, healthy subjects were examined for GI irritation following the administration of oral potassium for at least 7 days. Glycopyrrolate was coadministered to some subjects in order to study the additional effects of delayed gastric emptying. Results indicated that subjects administered wax-matrix tablets had the highest incidence of erosions (43%) and ulcers (11%). Evidence of GI irritation was less frequent among subjects receiving liquid (0%) and microencapsulated (10.5% erosions, 1.2% ulcers) formulations. Therefore, if oral potassium supplementation is necessary in a patient taking antimuscarinics, a liquid formulation should be considered. If a solid formulation is being prescribed, the patient should be counseled on strategies that can be used to avoid GI irritation such as taking potassium products only while seated or standing, remaining upright for 10 minutes after each dose, and ingesting each dose with plenty of fluids.
    Potassium-sparing diuretics: (Minor) Diuretics can increase urinary frequency, which may aggravate bladder symptoms.
    Pramlintide: (Major) Pramlintide therapy should not be considered in patients taking medications that alter gastric motility, such as anticholinergics. Pramlintide slows gastric emptying and the rate of nutrient delivery to the small intestine. Medications that have depressive effects on GI could potentiate the actions of pramlintide.
    Primidone: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Procainamide: (Moderate) The anticholinergic effects of procainamide may be significant and may be enhanced when combined with anticholinergics. Anticholinergic agents administered concurrently with procainamide may produce additive antivagal effects on AV nodal conduction, although this is not as well documented for procainamide as for quinidine.
    Prochlorperazine: (Moderate) Additive anticholinergic effects may be seen when anticholinergics are used concomitantly with phenothiazines, including prochlorperazine. 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.
    Promethazine: (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.
    Protease inhibitors: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Proton pump inhibitors: (Moderate) The American College of Gastroenterology states that the effectiveness of proton pump inhibitors (PPIs) may be theoretically decreased if given with other antisecretory agents (e.g., anticholinergics). Proton pump inhibitors (PPIs) inhibit only actively secreting H+-pumps.
    Pyridostigmine: (Moderate) Oxybutynin is an antimuscarinic; the muscarinic actions of pyridostigmine could be antagonized when used concomitantly with oxybutynin.
    Quazepam: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Quinidine: (Moderate) The anticholinergic effects of quinidine may be significant and may be enhanced when combined with antimuscarinics.
    Rasagiline: (Moderate) MAOIs exhibit secondary anticholinergic actions. Additive anticholinergic effects may be seen when MAOIs are used concomitantly with antimuscarinics. 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. Additive CNS effects are also possible when many of these drugs are combined with MAOIs.
    Remifentanil: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when remifentanil is used concomitantly with an anticholinergic drug. The concomitant use of remifentanil 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.
    Ribociclib: (Minor) Use caution if coadministration of ribociclib with oxybutynin is necessary, as the systemic exposure of oxybutynin may be increased resulting in increase in treatment-related adverse reactions; the clinical relevance of this interaction is unknown. Ribociclib is a moderate CYP3A4 inhibitor and oxybutynin is a CYP3A4 substrate.
    Ribociclib; Letrozole: (Minor) Use caution if coadministration of ribociclib with oxybutynin is necessary, as the systemic exposure of oxybutynin may be increased resulting in increase in treatment-related adverse reactions; the clinical relevance of this interaction is unknown. Ribociclib is a moderate CYP3A4 inhibitor and oxybutynin is a CYP3A4 substrate.
    Rifabutin: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as rifamycins, may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Rifampin: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as rifamycins, may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Rifamycins: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as rifamycins, may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Rifapentine: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as rifamycins, may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Ritonavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Rivastigmine: (Moderate) The therapeutic benefits of rivastigmine, 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.
    Saquinavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Secobarbital: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Secretin: (Major) Discontinue anticholinergic medications at least 5 half-lives before administering secretin. Patients who are receiving anticholinergics at the time of stimulation testing may be hyporesponsive to secretin stimulation and produce a false result. Consider additional testing and clinical assessments for aid in diagnosis.
    Sedating H1-blockers: (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.
    Simeprevir: (Moderate) Simeprevir, a mild intestinal CYP3A4 inhibitor, may increase the side effects of oxybutynin, which is a CYP3A4 substrate. Monitor patients for adverse effects of oxybutynin, such as CNS and anticholinergic effects.
    Sincalide: (Moderate) Sincalide-induced gallbladder ejection fraction may be affected by anticholinergics. False study results are possible in patients with drug-induced hyper- or hypo-responsiveness; thorough patient history is important in the interpretation of procedure results.
    Sodium Bicarbonate: (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.
    Solifenacin: (Moderate) Additive anticholinergic effects may be seen when drugs with antimuscarinic properties like solifenacin are used concomitantly with other antimuscarinics. Blurred vision and dry mouth would be common effects. 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.
    St. John's Wort, Hypericum perforatum: (Moderate) Oxybutynin is metabolized by CYP3A4; drugs that induce CYP3A4, such as St. John's Wort, may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Streptogramins: (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme, such as streptogramins, may increase the serum concentrations of oxybutynin. The manufacturer recommends caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Sufentanil: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when sufentanil is used concomitantly with an anticholinergic drug. The concomitant use of sufentanil 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.
    Sunscreens: (Moderate) The effect on the pharmacokinetics of oxybutynin topical gel when sunscreens were applied 30 minutes before or after oxybutynin gel was evaluated in a single-dose randomized crossover study (n=16). The study revealed no difference in the absorption of oxybutynin gel when applied in this manner. However, the effects of sunscreen on oxybutynin absorption when used within 30 minutes of gel application have not been studied. Therefore, the manufacturer recommends that patients use sunscreen either 30 minutes before or after gel application.
    Tacrine: (Moderate) The therapeutic benefits of tacrine, 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.
    Tapentadol: (Moderate) Tapentadol should be used cautiously with anticholinergic medications since additive depressive effects on GI motility or bladder function may occur. Monitor patients for signs of urinary retention or reduced gastric motility. 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. Opiate analgesics combined with antimuscarinics can cause severe constipation or paralytic ileus, especially with chronic use. Additive CNS effects like drowsiness or dizziness may also occur.
    Tegaserod: (Major) Drugs that exert significant anticholinergic properties such as antimuscarinics may pharmacodynamically oppose the effects of prokinetic agents such as tegaserod. Avoid administering antimuscarinics along with tegaserod under most circumstances. Inhaled respiratory antimuscarinics, such as ipratropium, are unlikely to interact with tegaserod. Ophthalmic anticholinergics may interact if sufficient systemic absorption of the eye medication occurs.
    Telaprevir: (Moderate) Close clinical monitoring is advised when administering oxybutynin with telaprevir due to an increased potential for oxybutynin-related adverse events. If oxybutynin dose adjustments are made, re-adjust the dose upon completion of telaprevir treatment. Although this interaction has not been studied, predictions about the interaction can be made based on the metabolic pathway of oxybutynin. Oxybutynin is partially metabolized by the hepatic isoenzyme CYP3A4; telaprevir inhibits this isoenzyme. Coadministration may result in elevated oxybutynin plasma concentrations.
    Telithromycin: (Moderate) Concentrations of oxybutynin may be increased with concomitant use of telithromycin. Oxybutynin is a CYP3A4 substrate and telithromycin is a strong CYP3A4 inhibitor. Patients should be monitored for increased side effects.
    Telotristat Ethyl: (Moderate) Use caution if coadministration of telotristat ethyl and oxybutynin is necessary, as the systemic exposure of oxybutynin may be decreased resulting in reduced efficacy. If these drugs are used together, monitor patients for suboptimal efficacy of oxybutynin; consider increasing the dose of oxybutynin if necessary. Oxybutynin is a CYP3A4 substrate. The mean Cmax and AUC of another sensitive CYP3A4 substrate was decreased by 25% and 48%, respectively, when coadministered with telotristat ethyl; the mechanism of this interaction appears to be that telotristat ethyl increases the glucuronidation of the CYP3A4 substrate.
    Temazepam: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Thiazide diuretics: (Minor) Coadministration of thiazides and antimuscarinics (e.g., atropine and biperiden) may result in increased bioavailability of the thiazide. This is apparently a result of a decrease in gastrointestinal motility and rate of stomach emptying by the antimuscarinic agent. In addition, diuretics can increase urinary frequency, which may aggravate bladder symptoms.
    Thiopental: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics. In addition, because oxybutynin is metabolized by CYP3A4, administration with drugs that induce CYP3A4 (such as barbiturates) may reduce the serum concentration and effects of oxybutynin. Patients receiving these drugs concomitantly should be monitored for reduced efficacy.
    Thiothixene: (Moderate) Anticholinergics may have additive effects with thiothixene, an antipsychotic with the potential for anticholinergic activity. Monitor for anticholinergic-related adverse effects such as xerostomia, blurred vision, constipation, and urinary retention during concurrent use.
    Tiotropium: (Moderate) Although tiotropium is minimally absorbed into the systemic circulation after inhalation, tiotropium may have additive anticholinergic effects when administered with other antimuscarinics. Per the manufacturer, avoid concomitant administration of tiotropium with other anticholinergic medications when possible.
    Tiotropium; Olodaterol: (Moderate) Although tiotropium is minimally absorbed into the systemic circulation after inhalation, tiotropium may have additive anticholinergic effects when administered with other antimuscarinics. Per the manufacturer, avoid concomitant administration of tiotropium with other anticholinergic medications when possible.
    Tipranavir: (Moderate) Oxybutynin is metabolized by CYP3A4. Caution should be used when oxybutynin is given in combination with inhibitors of CYP3A4, such as protease inhibitors. Monitor for adverse effects if these drugs are administered together.
    Tolterodine: (Moderate) Additive anticholinergic effects may be seen when tolterodine is used concomitantly with other antimuscarinics. When possible, avoid concurrent use, especially in the elderly, who are more susceptible to the anticholinergic effects. Consider alternatives to these other medications, if available. Clinicians should note that antimuscarinic effects might be seen not only on bladder smooth muscle, but also on GI function, the eye, and temperature regulation. Blurred vision, constipation, and dry mouth may be more prominent additive effects. With many of the listed agents, additive drowsiness may also occur when combined.
    Topiramate: (Moderate) Use caution if carbonic anhydrase inhibitors are administered with anticholinergics and monitor for excessive anticholinergic adverse effects. The use of topiramate with agents that may increase the risk for heat-related disorders, such as anticholinergics, may lead to oligohidrosis, hyperthermia and/or heat stroke.
    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.
    Trandolapril; Verapamil: (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme, such as verapamil, may increase the serum concentrations of oxybutynin. The manufacturer recommends caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Triazolam: (Moderate) Additive CNS depression may occur when oxybutynin is used concomitantly with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics.
    Tricyclic antidepressants: (Moderate) Depending on the specific agent, additive anticholinergic effects may be seen when tricyclic antidepressants (TCAs) are used concomitantly with other anticholinergics. 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 many of these drugs are combined with tricyclic antidepressants.
    Trifluoperazine: (Moderate) Additive anticholinergic effects may be seen when anticholinergics are used concomitantly with phenothiazines, including trifluoperazine. 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.
    Trimethobenzamide: (Moderate) Trimethobenzamide has CNS depressant effects and may cause drowsiness. The concurrent use of trimethobenzamide with other medications that cause CNS depression, like the anticholinergics, may potentiate the effects of either trimethobenzamide or the anticholinergic.
    Triprolidine: (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.
    Trospium: (Moderate) Additive anticholinergic effects may be seen when trospium is used concomitantly with other antimuscarinics. When possible, avoid concurrent use, especially in the elderly, who are more susceptible to the anticholinergic effects. Consider alternatives to these other medications, if available. Clinicians should note that antimuscarinic effects might be seen not only on bladder smooth muscle, but also on GI function, the eye, and temperature regulation. Blurred vision, constipation, and dry mouth may be more prominent additive effects. With many of the listed agents, additive drowsiness may also occur when combined with trospium.
    Umeclidinium: (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.
    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.
    Vemurafenib: (Moderate) Vemuraifenib is an inducer of CYP3A4 and decreased plasma concentrations of drugs metabolized by this enzyme, such as oxybutynin, could be expected with concurrent use. Use caution, and monitor therapeutic effects of oxybutynin when coadministered with vemurafenib.
    Verapamil: (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme, such as verapamil, may increase the serum concentrations of oxybutynin. The manufacturer recommends caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Voriconazole: (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme, such as voriconazole, may increase the serum concentrations of oxybutynin. The manufacturer recommends caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Zafirlukast: (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme, such as zafirlukast, may increase the serum concentrations of oxybutynin. The manufacturer recommends caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Zaleplon: (Moderate) Oxybutynin causes CNS-depressant effects including somnolence and drowsiness; concurrent use with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics, can increase the total sedative effects of oxybutynin.
    Zileuton: (Moderate) Oxybutynin is metabolized by CYP3A4. Inhibitors of the CYP3A4 enzyme, such as zileuton, may increase the serum concentrations of oxybutynin. The manufacturer recommends caution when oxybutynin is co-administered with CYP3A4 inhibitors.
    Zolpidem: (Moderate) Oxybutynin causes CNS-depressant effects including somnolence and drowsiness; concurrent use with other CNS-depressant drugs, including anxiolytics, sedatives, and hypnotics, can increase the total sedative effects of oxybutynin.
    Zonisamide: (Moderate) Zonisamide use is associated with case reports of decreased sweating, hyperthermia, heat intolerance, or heat stroke and should be used with caution in combination with other drugs that may also predispose patients to heat-related disorders like anticholinergics.

    PREGNANCY AND LACTATION

    Pregnancy

    There are no adequate and well-controlled studies of topical or oral oxybutynin use in human pregnancy. Subcutaneous administration to rats at doses up to 25 mg/kg (approximately 50 times the human exposure based on surface area) and to rabbits at doses up to 0.4 mg/kg (approximately 1 times the human exposure) revealed no evidence of harm to the fetus due to oxybutynin. Reproduction studies with oxybutynin in the mouse, rat, hamster, and rabbit showed no evidence of impaired fertility. Oxybutynin should not be given to pregnant women unless, in the judgment of the physician, the probable clinical benefits outweigh the possible risks.

    It is not known if oxybutynin is excreted in breast milk. Because many drugs are excreted in human milk, caution should be exercised when oxybutynin is administered to a nursing woman. Because an infant is usually very sensitive to anticholinergic effects of drugs, there may be a risk for adverse effects if the infant is exposed to oxybutynin via breast-feeding. Lactation suppression has been reported during postmarketing use of immediate-release oxybutynin. 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 administered drug, healthcare providers are encouraged to report the adverse effect to the FDA.

    MECHANISM OF ACTION

    Mechanism of Action: Oxybutynin is a tertiary amine ester that exerts antimuscarinic (atropine-like) and antispasmodic (papaverine-like) actions on smooth muscle. While the antimuscarinic effect is significantly less than for atropine, the antispasmodic activity is considerably greater than that of atropine, producing an effect on the detrusor muscle 4 to 10 times that of atropine. Oxybutynin does not appear to affect the smooth muscle of the blood vessels as does papaverine.Oxybutynin is a bladder muscle relaxant, and it suppresses the urge to void. Oxybutynin inhibits involuntary detrussor muscle contractions caused by detrusor muscle instability (non-neurogenic) or detrusor muscle hyperreflexia (e.g., as occurs in neurogenic disorders). Reduced contractions allow the bladder to relax and increase its visceral capacity. Oxybutynin thus decreases urgency by delaying the initial desire to void. Oxybutynin's effects on the detrusor muscle are mediated via M3 receptors. However, oxybutynin is a non-selective antimuscarinic and may produce side effects consistent with anticholinergic actions in the CNS, parotid glands, and GI tract. Oxybutynin also possesses minor local anesthetic properties.

    PHARMACOKINETICS

    Oxybutynin is administered topically as a transdermal patch or gel and orally.
     
    Once in the systemic circulation, oxybutynin is widely distributed to body tissues. Distribution of oxybutynin is not well characterized, however, oxybutynin has an affinity for anticholinergic receptors in the urinary tract, salivary glands, and CNS. Oxybutynin exhibits dose-dependent, linear pharmacokinetics.
     
    The metabolite desethyloxybutynin is active and is equipotent to oxybutynin with respect to its antimuscarinic actions. A second metabolite, phenylcyclohexylglycolic acid, is inactive. The elimination half-life (half-life) of oxybutynin is 2—5 hours. Less than 0.1% of oxybutynin or desethyloxybutynin appears in the urine unchanged.

    Oral Route

    Following oral administration of immediate-release oxybutynin dosage forms, absorption from the gut is rapid, with peak concentrations occurring at 1 hour. Antispasmodic activity occurs within 30—60 minutes of administration and can last for 6—10 hours. Administration of an oral controlled-release formulation (i.e., Ditropan XL), results in a Cmax at 4—6 hours and consistent 24-hour plasma-concentrations at steady-state. Coadministration of oxybutynin solution with food results in a slight delay in absorption and a 25% increase in bioavailability. Oxybutynin is widely distributed in body tissues following systemic absorption. Oxybutynin enantiomers are highly bound (>99%) to plasma proteins. Both enantiomers of desethyloxybutynin are also highly bound (>97%). The major binding protein is alpha-1 acid glycoprotein. After oral administration, oxybutynin is extensively metabolized via the enteric and hepatic CYP450 3A4 isoenzymes.

    Topical Route

    Topical Gels: Absorption of oxybutynin topical gel is similar after application to the abdomen, upper arm/shoulders or thighs. Steady-state concentrations are achieved within 3 to 7 days of continuous daily dosing.
     
    Transdermal System: The transdermal patch (Oxytrol) delivers 3.9 mg/day of oxybutynin through the skin by passive diffusion. Absorption of oxybutynin is bioequivalent after application of the patch to the abdomen, buttocks, or hips. Plasma concentrations increase for approximately 24—48 hours after patch application; steady-state concentrations are maintained for up to 96 hours. Transdermal administration of oxybutynin bypasses enteric and hepatic first-pass metabolism. Since the skin contains only small amounts of CYP3A4, limited pre-systemic metabolism occurs with transdermal administration.