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  • CLASSES

    Mixed Opiate Agonist-Antagonist

    BOXED WARNING

    Asthma, chronic obstructive pulmonary disease (COPD), coadministration with other CNS depressants, pulmonary disease, respiratory depression, respiratory insufficiency

    Do not use pentazocine in patients with existing respiratory depression. Although the risk is lower than with morphine, moderate therapeutic doses of pentazocine may significantly decrease pulmonary ventilation. Avoid coadministration with other CNS depressants when possible as this significantly increases the risk for respiratory depression, low blood pressure, and death. Therefore, pentazocine should be used with caution in patients with known pulmonary disease such as bronchial asthma, chronic obstructive pulmonary disease (COPD), or respiratory insufficiency due to limited respiratory reserve.

    DEA CLASS

    Rx, schedule IV

    DESCRIPTION

    Synthetic opiate agonist-antagonist analgesic
    One-sixth to one-third as potent as morphine
    Less incidence of adverse reactions than with morphine and other opiates

    COMMON BRAND NAMES

    Talwin

    HOW SUPPLIED

    Talwin Intramuscular Inj Sol: 1mL, 30mg
    Talwin Intravenous Inj Sol: 1mL, 30mg
    Talwin Subcutaneous Inj Sol: 1mL, 30mg

    DOSAGE & INDICATIONS

    For the treatment of moderate pain to severe pain.
    NOTE: Parenteral pentazocine 20 mg to 40 mg is reported to be equianalgesic to parenteral morphine 10 mg or parenteral meperidine 75 mg to 100 mg.
    NOTE: Do not abruptly discontinue prolonged therapy as withdrawal symptoms may occur; taper dosing as appropriate.
    For severe pain during labor.
    Intramuscular or Intravenous dosage
    Adults and Adolescents

    Commonly, 30 mg IM as a single dose has been given. 20 mg IV gives adequate relief to some patients in labor when contractions become regular; may repeat every 2 to 3 hours, as needed, for a total of 2 to 3 doses.

    Intravenous, Intramuscular, or Subcutaneous dosage

    NOTE: Only use the subcutaneous route when necessary because of the possibility of severe tissue damage at injection sites. If frequent injections are needed, administer intramuscularly and rotate injection sites.

    Adults

    30 mg IV/IM/subcutaneously every 3 to 4 hours, as needed. Doses greater than 30 mg IV or greater than 60 mg IM/subcutaneously are not recommended. Do not exceed 360 mg/day. Because of increased sensitivity to analgesic effects, initiate with low doses in geriatric patients.

    Adolescents† and Children 9 years or more†

    Limited data suggest 30 mg IM (single dose) may be effective for postoperative pain.

    Children 5 to 8 years†

    Limited data suggest 15 mg IM (single dose) may be effective for postoperative pain.

    For preanesthesia medication, as well as adjunctive use in general anesthesia induction and general anesthesia maintenance.
    Intramuscular, Intravenous, or Subcutaneous dosage

    NOTE: Because of risk of severe tissue damage at injection sites, limit subcutaneous administration to only when necessary (IM administration is preferred), and rotate injection sites if multiple doses are needed.

    Adults and Adolescents 17 years

    30 mg IM/IV/subcutaneously as a single dose. May repeat every 3 to 4 hours as needed; use IM route for frequent dosing. Doses greater than 30 mg IV or greater than 60 mg IM/subcutaneously are not recommended. Do not exceed 360 mg/day. Initiate with low doses in geriatric patients.

    Adolescents 16 years and younger and Children

    0.5 mg/kg IM for a single dose; do not exceed 30 mg.

    MAXIMUM DOSAGE

    Adults

    360 mg/day IV/IM/SQ, not to exceed 30 mg/dose IV or 60 mg/dose IM/SQ.

    Geriatric

    360 mg/day IV/IM/SQ, not to exceed 30 mg/dose IV or 60 mg/dose IM/SQ.

    Adolescents

    17 years: 360 mg/day IV/IM/SQ, not to exceed 30 mg/dose IV or 60 mg/dose IM/SQ.
    < 17 years: 0.5 mg/kg IM (up to 30 mg) x1 dose.

    Children

    0.5 mg/kg IM (up to 30 mg) x1 dose.

    Infants

    Safety and efficacy have not been established.

    Neonates

    Safety and efficacy have not been established.

    DOSING CONSIDERATIONS

    Hepatic Impairment

    Dosage should be modified depending on clinical response and degree of hepatic impairment, but no quantitative recommendations are available. If repeated doses are required, the dosing interval should be lengthened or the dosage reduced.

    Renal Impairment

    CrCl > 50 ml/min: no dosage adjustment required.
    CrCl 10—50 ml/min: reduce dose by 25%.
    CrCl < 10 ml/min: reduce dose by 50%.

    ADMINISTRATION

    Injectable Administration

    May be administered by intravenous, intramuscular, or subcutaneous injection. However, the subcutaneous route should be used only when necessary, due to possible severe damage at injection sites.
    No dilution is necessary.
    Visually inspect parenteral products for particulate matter and discoloration prior to administration whenever solution and container permit.

    Intravenous Administration

    Inject directly into a vein or into tubing of a free-flowing compatible IV infusion.

    Intramuscular Administration

    Inject deeply into a large muscle mass. Aspirate prior to injection to avoid injection into a blood vessel.
    Rotation of intramuscular injection sites (e.g., upper outer quadrants of the buttocks, mid-lateral aspects of the thighs, and the deltoid areas) is essential to decrease risk of severe tissue damage at injection sites.

    Subcutaneous Administration

    Administer subcutaneously only when necessary, as there is the possibility of severe tissue damage at injection sites. When frequent injections are needed, administer intramuscularly.
    Rotation of injection sites (e.g., upper outer quadrants of the buttocks, mid-lateral aspects of the thighs, and the deltoid areas) is essential to reduce the risk of tissue damage.

    STORAGE

    Talwin:
    - Store at controlled room temperature (between 68 and 77 degrees F)

    CONTRAINDICATIONS / PRECAUTIONS

    Acute abdomen, constipation, GI disease, GI obstruction, ileus, inflammatory bowel disease, ulcerative colitis

    Despite having weak effects on GI motility when compared to other opiate agonists, pentazocine should be used cautiously in patients with GI disease, including GI obstruction or ileus, ulcerative colitis, or pre-existing constipation. Patients with acute ulcerative colitis (UC) or other inflammatory bowel disease may be more sensitive to the constipating effects of opiate agonists. Pentazocine, like other opioids, may also obscure the diagnosis or clinical course in patients with an acute abdomen. Although opiate agonists are usually contraindicated for use in patients with diarrhea secondary to poisoning or infectious diarrhea, antimotility agents have been used successfully in these patients. If possible, pentazocine should not be given until the toxic substance has been eliminated.

    Acute intoxication of CNS depressants, alcoholism, ethanol intoxication, substance abuse

    Use pentazocine with caution, if at all, in patients with a history of or with active substance abuse or dependence. Opioid-dependent patients may experience withdrawal symptoms following administration of pentazocine, a mixed opioid agonist-antagonist, while those with a history of dependence may be at higher risk of developing psychologic dependence to pentazocine. This may lead to substance abuse in some patients. Take precautions to avoid patient-initiated increases in dosage with all patients. Patients experiencing ethanol intoxication or delirium tremens, or acute intoxication of CNS depressants, may be at increased risk of adverse events if administered pentazocine; CNS depressant effects are additive. The indication for use of pentazocine in patients with a history of alcoholism or drug dependence is for the treatment of moderate to severe pain. This medication is not approved for the management of substance abuse (alcohol or drug dependence).

    Abrupt discontinuation

    Abrupt discontinuation of prolonged pentazocine therapy may result in withdrawal symptoms. Patients should be gradually tapered off pentazocine to avoid a withdrawal reaction.

    Asthma, chronic obstructive pulmonary disease (COPD), coadministration with other CNS depressants, pulmonary disease, respiratory depression, respiratory insufficiency

    Do not use pentazocine in patients with existing respiratory depression. Although the risk is lower than with morphine, moderate therapeutic doses of pentazocine may significantly decrease pulmonary ventilation. Avoid coadministration with other CNS depressants when possible as this significantly increases the risk for respiratory depression, low blood pressure, and death. Therefore, pentazocine should be used with caution in patients with known pulmonary disease such as bronchial asthma, chronic obstructive pulmonary disease (COPD), or respiratory insufficiency due to limited respiratory reserve.

    Head trauma, increased intracranial pressure, intracranial mass, seizure disorder, seizures

    Patients predisposed to seizures or with head trauma, an intracranial mass, or increased intracranial pressure should only be given pentazocine if the benefits outweigh the risks. Pentazocine can compromise the evaluation of neurologic parameters. Respiratory depression can produce cerebral hypoxia and raise both cerebrospinal fluid (via vasodilation following CO2 retention) and intracranial pressures, exaggerating the injury. Patients with a seizure disorder should be treated with pentazocine cautiously. Seizures have occurred in a few patients in association with pentazocine use.

    Acute myocardial infarction, angina, cardiac disease, heart failure, ventricular dysfunction

    Patients with cardiac disease should be treated with caution. Pentazocine can increase blood pressure (possibly through the release of endogenous catecholamines) and cardiac workload, so its use in patients with acute myocardial infarction, ventricular dysfunction, or coronary insufficiency (i.e., angina, heart failure) must be carefully evaluated.

    Hepatic disease, renal failure, renal impairment

    Drug accumulation can occur in patients with renal impairment, renal failure, or hepatic disease, prolonging pentazocine's duration of action and increasing the risk for adverse reactions.

    Geriatric

    Geriatric patients may be more sensitive to the analgesic effects of pentazocine as compared to younger patients. If therapy is undertaken, the manufacturer recommends low initial dosing and close observation. According to the Beers Criteria, pentazocine is considered a potentially inappropriate medication (PIM) for use in geriatric patients and should be avoided because there is an increased incidence of adverse central nervous system (CNS) effects (e.g., confusion, hallucinations) compared to other commonly prescribed opioid analgesics and there are safer alternatives available. The federal Omnibus Budget Reconciliation Act (OBRA) regulates medication use in residents of long-term care facilities (LTCFs). According to OBRA, pentazocine has limited effectiveness because it is a partial opiate agonist-antagonist, and is not recommended for use in older adults. In addition, pentazocine causes CNS side effects (e.g., confusion, hallucinations) more commonly than other opioid analgesics, and may also cause dizziness, lightheadedness, euphoria, sedation, hypotension, tachycardia, and syncope.

    Intramuscular injections, parenteral administration, potential for overdose or poisoning, subcutaneous administration

    Inform patients of the potential for overdose or poisoning associated with pentazocine use. Advise patients to not exceed prescribed dosing, to avoid interacting medications, and to avoid intentional misuse. Should overdosage occur, adequate measures to maintain ventilation and general circulatory support, such as assisted or controlled ventilation, intravenous fluids, vasopressors, and other supportive measures should be employed as indicated. Consideration should be given to gastric lavage and gastric aspiration. For respiratory depression due to overdosage or unusual sensitivity to pentazocine, parenteral naloxone is a specific and effective antagonist. Anti-convulsant therapy may also be necessary. Patients who have received multiple injections of pentazocine lactate injection solution have developed severe sclerosis of the skin, subcutaneous tissues, and underlying muscle at the site of injection (i.e., with parenteral administration, subcutaneous injections, and intramuscular injections). Therefore, constant rotation of injection sites is essential. Additionally, due to the risk of tissue damage, subcutaneous administration should be used only when necessary; when frequent injections are needed, administer intramuscularly.

    Labor, obstetric delivery, pregnancy

    Pentazocine is classified as FDA pregnancy risk category C. Patients receiving injectable pentazocine during labor have experienced no adverse effects other than those that occur with commonly used analgesics. Use with caution during the obstetric delivery of premature infants. Administration during obstetric delivery may result in respiratory depression in the newborn, and pentazocine can cross the placental barrier and also cause central nervous system depression in the newborn. Outside of labor and delivery, pentazocine should be used during pregnancy only if clearly needed. Animal studies have not demonstrated teratogenic or embryotoxic effects. There have been rare reports of possible abstinence syndromes and symptoms of withdrawal in newborns after prolonged or regular use during pregnancy.

    Breast-feeding

    According to the manufacturer, pentazocine is excreted in human milk and cautious use is advised in women who are breast-feeding. Alternative analgesics that are considered to be usually compatible with breast-feeding by the American Academy of Pediatrics (AAP) include acetaminophen, ibuprofen, indomethacin, naproxen, piroxicam, and morphine. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally ingested drug, healthcare providers are encouraged to report the adverse effect to the FDA.

    Infants, neonates

    Parenteral pentazocine is indicated for use in children 1 year of age and older; safety and efficacy have not been established in neonates and infants.

    Opiate agonist hypersensitivity, sulfite hypersensitivity

    Pentazocine use is contraindicated in patients with known pentazocine hypersensitivity. Use of bisulfite-containing multi-dose pentazocine injection is contraindicated in patients with sulfite hypersensitivity. Sulfite hypersensitivity is more common in patients with asthma. Patients who have experienced a true opiate agonist hypersensitivity may be more likely to experience an allergic reaction, so use caution in using pentazocine in such patients. However, cross-sensitivity of pentazocine with other opiate agonists or mixed opiate agonist-antagonists is not generally documented.

    Driving or operating machinery

    Patients should be warned that pentazocine can impair the mental and physical abilities required for the performance of potentially dangerous tasks, such as driving or operating machinery. These effects may persist for varying periods of time after dosing.

    Tobacco smoking

    Tobacco smoking is associated with increased hepatic metabolism of pentazocine, potentially reducing the clinical effectiveness of a standard dose. Conversely, sudden smoking cessation may cause an increase in the therapeutic effects of pentazocine as hepatic enzyme activities return to normal, despite the use of nicotine replacement products.

    MAOI therapy

    Concomitant use of monoamine oxidase inhibitors (MAOIs) with pentazocine may cause CNS excitation and hypertension through their respective effects on catecholamines. Caution should be observed when administering pentazocine to a patient who is currently receiving MAOI therapy or who has received it within the preceding 14 days.

    Porphyria

    Particular caution should be exercised in administering pentazocine to patients with porphyria, as it may provoke an acute attack in susceptible individuals.

    Biliary tract disease, cholestasis, pancreatitis

    Use pentazocine with caution in patients with cholecystitis and/or cholestasis or pancreatitis. Safe use in patients with biliary tract disease or undergoing biliary tract surgery has not been established. Although biliary tract spasm has been reported with pentazocine use, some evidence suggests that pentazocine, unlike other opioids, may cause little or no elevation in biliary tract pressures. The clinical significance of these findings, however, is not known.

    Adrenal insufficiency, hypothyroidism, myxedema, prostatic hypertrophy

    Use pentazocine with caution in patients with adrenal insufficiency (i.e., Addison's disease), hypothyroidism, myxedema, or prostatic hypertrophy. Such patients may be at increased risk of adverse events. Opioids inhibit the secretion of adrenocorticotropic hormone (ACTH), cortisol, and luteinizing hormone (LH); however, the thyroid stimulating hormone may be either stimulated or inhibited by opioids. Rarely, adrenal insufficiency has been reported in association with opioid use. Patients should seek immediate medical attention if they experience symptoms such as nausea, vomiting, loss of appetite, fatigue, weakness, dizziness, or hypotension. If adrenocortical insufficiency is suspected, confirm with diagnostic testing as soon as possible. If diagnosed, the patient should be treated with physiologic replacement doses of corticosteroids, and if appropriate, weaned off of opioid therapy. If the opioid can be discontinued, a follow-up assessment of adrenal function should be performed to determine if corticosteroid treatment can be discontinued. Other opioids may be tried; some cases reported use of a different opioid with no recurrence of adrenocortical insufficiency. It is unclear which, if any, opioids are more likely to cause adrenocortical insufficiency. In addition, chronic opioid use may lead to symptoms of hypogonadism, resulting from changes in the hypothalamic-pituitary-gonadal axis. Monitor patients for symptoms of opioid-induced endocrinopathy, particularly those receiving a daily dose equivalent to 100 mg or more of morphine. Patients presenting with signs or symptoms of androgen deficiency should undergo laboratory evaluation.

    ADVERSE REACTIONS

    Severe

    increased intracranial pressure / Early / Incidence not known
    seizures / Delayed / Incidence not known
    toxic epidermal necrolysis / Delayed / Incidence not known
    angioedema / Rapid / Incidence not known
    Stevens-Johnson syndrome / Delayed / Incidence not known
    erythema multiforme / Delayed / Incidence not known
    anaphylactic shock / Rapid / Incidence not known
    neonatal abstinence syndrome / Early / Incidence not known
    apnea / Delayed / Incidence not known
    neonatal respiratory depression / Rapid / Incidence not known
    serotonin syndrome / Delayed / Incidence not known
    SIADH / Delayed / Incidence not known

    Moderate

    confusion / Early / 1.0-10.0
    tolerance / Delayed / 1.0-10.0
    dysphoria / Early / Incidence not known
    hallucinations / Early / Incidence not known
    depression / Delayed / Incidence not known
    euphoria / Early / Incidence not known
    respiratory depression / Rapid / Incidence not known
    dyspnea / Early / Incidence not known
    constipation / Delayed / Incidence not known
    hypertension / Early / Incidence not known
    sinus tachycardia / Rapid / Incidence not known
    hypotension / Rapid / Incidence not known
    skin ulcer / Delayed / Incidence not known
    eosinophilia / Delayed / Incidence not known
    leukopenia / Delayed / Incidence not known
    neutropenia / Delayed / Incidence not known
    nystagmus / Delayed / Incidence not known
    blurred vision / Early / Incidence not known
    urinary retention / Early / Incidence not known
    uterine contractions / Early / Incidence not known
    psychological dependence / Delayed / Incidence not known
    withdrawal / Early / Incidence not known
    physiological dependence / Delayed / Incidence not known
    infertility / Delayed / Incidence not known
    impotence (erectile dysfunction) / Delayed / Incidence not known
    hyponatremia / Delayed / Incidence not known
    adrenocortical insufficiency / Delayed / Incidence not known

    Mild

    dizziness / Early / 1.0-10.0
    nausea / Early / 1.0-10.0
    vomiting / Early / 1.0-10.0
    drowsiness / Early / 10.0
    tinnitus / Delayed / Incidence not known
    irritability / Delayed / Incidence not known
    tremor / Early / Incidence not known
    paresthesias / Delayed / Incidence not known
    insomnia / Early / Incidence not known
    headache / Early / Incidence not known
    weakness / Early / Incidence not known
    anorexia / Delayed / Incidence not known
    xerostomia / Early / Incidence not known
    dysgeusia / Early / Incidence not known
    diarrhea / Early / Incidence not known
    abdominal pain / Early / Incidence not known
    syncope / Early / Incidence not known
    flushing / Rapid / Incidence not known
    pruritus / Rapid / Incidence not known
    urticaria / Rapid / Incidence not known
    scleral induration / Delayed / Incidence not known
    rash (unspecified) / Early / Incidence not known
    injection site reaction / Rapid / Incidence not known
    miosis / Early / Incidence not known
    diplopia / Early / Incidence not known
    hyperhidrosis / Delayed / Incidence not known
    chills / Rapid / Incidence not known
    libido decrease / Delayed / Incidence not known
    gonadal suppression / Delayed / Incidence not known
    amenorrhea / Delayed / Incidence not known

    DRUG INTERACTIONS

    Acetaminophen; Butalbital: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Acetaminophen; Butalbital; Caffeine: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Acetaminophen; Butalbital; Caffeine; Codeine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as codeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of mu-receptor opiate agonists and reduce analgesic effects of codeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist. (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Acetaminophen; Caffeine; Dihydrocodeine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as dihydrocodeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce the analgesic effects of dihydrocodeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Acetaminophen; Codeine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as codeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of mu-receptor opiate agonists and reduce analgesic effects of codeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Acetaminophen; Hydrocodone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Acetaminophen; Oxycodone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as oxycodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of oxycodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Acetaminophen; Propoxyphene: (Major) Pentazocine may partially block the analgesic, respiratory depressant and CNS depressant effects of pure opiate agonists. Due to their antagonistic properties, pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists.
    Acetaminophen; Tramadol: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as tramadol. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. There is also a potential increased risk of seizures if tramadol and pentazocine are given concurrently. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Alfentanil: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as alfentanil. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Alprazolam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Amantadine: (Moderate) Use pentazocine with caution in any patient receiving anticholinergic agents. Coadministration of pentazocine with amantadine may result in additive anticholinergic effects, such as urinary retention and constipation.
    Amitriptyline; Chlordiazepoxide: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Amobarbital: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Amoxapine: (Moderate) Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity. Coadministration of pentazocine with amoxapine may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation.
    Anticholinergics: (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.
    Aripiprazole: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Asenapine: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Aspirin, ASA; Butalbital; Caffeine: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Aspirin, ASA; Butalbital; Caffeine; Codeine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as codeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of mu-receptor opiate agonists and reduce analgesic effects of codeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist. (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Aspirin, ASA; Caffeine; Dihydrocodeine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as dihydrocodeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce the analgesic effects of dihydrocodeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Aspirin, ASA; Carisoprodol; Codeine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as codeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of mu-receptor opiate agonists and reduce analgesic effects of codeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Aspirin, ASA; Oxycodone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as oxycodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of oxycodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Atropine: (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.
    Atropine; Benzoic Acid; Hyoscyamine; Methenamine; Methylene Blue; Phenyl Salicylate: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when pentazocine is used concomitantly with an anticholinergic drug. The concomitant use of pentazocine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) Theoretically, concurrent use of methylene blue and pentazocine may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and pentazocine increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Atropine; Difenoxin: (Major) Pentazocine may partially block the analgesic, respiratory depressant and CNS depressant effects of pure opiate agonists. Due to their antagonistic properties, pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Pentazocine may also be used concurrently with some opiate agonists and cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of pure opiate agonist used; antagonistic effects are more common at low to moderate doses of the pure opiate agonist. For example, some patients who received methadone for the daily treatment of narcotic dependence have experienced withdrawal symptoms after receiving pentazocine. Withdrawal symptoms may include anxiety, agitation, mood changes, hallucinations, dysphoria, weakness, and diarrhea. (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.
    Atropine; Diphenoxylate: (Major) Pentazocine may partially block the analgesic, respiratory depressant and CNS depressant effects of pure opiate agonists. Due to their antagonistic properties, pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Pentazocine may also be used concurrently with some opiate agonists and cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of pure opiate agonist used; antagonistic effects are more common at low to moderate doses of the pure opiate agonist. For example, some patients who received methadone for the daily treatment of narcotic dependence have experienced withdrawal symptoms after receiving pentazocine. Withdrawal symptoms may include anxiety, agitation, mood changes, hallucinations, dysphoria, weakness, and diarrhea. (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.
    Atropine; Edrophonium: (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.
    Atropine; Hyoscyamine; Phenobarbital; Scopolamine: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates. (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.
    atypical antipsychotic: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Azelastine: (Moderate) An enhanced CNS depressant effect may occur when azelastine is combined with other CNS depressants including pentazocine.
    Azelastine; Fluticasone: (Moderate) An enhanced CNS depressant effect may occur when azelastine is combined with other CNS depressants including pentazocine.
    Barbiturates: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Belladonna Alkaloids; Ergotamine; Phenobarbital: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates. (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.
    Belladonna; Opium: (Major) Pentazocine may partially block the analgesic, respiratory depressant and CNS depressant effects of pure opiate agonists. Pentazocine may also be used concurrently with some opiate agonists and cause additive CNS, respiratory, and hypotensive effects. (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.
    Benzoic Acid; Hyoscyamine; Methenamine; Methylene Blue; Phenyl Salicylate: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when pentazocine is used concomitantly with an anticholinergic drug. The concomitant use of pentazocine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) Theoretically, concurrent use of methylene blue and pentazocine may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and pentazocine increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Benztropine: (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.
    Brexpiprazole: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    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.
    Brompheniramine; Guaifenesin; Hydrocodone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Brompheniramine; Hydrocodone; Pseudoephedrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Buprenorphine: (Major) Concomitant use of buprenorphine with other CNS depressants can lead to additive CNS depressive effects. Hypotension, profound sedation, coma, respiratory depression, or death may occur. Prior to concurrent use of buprenorphine in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. A dose reduction of one or both drugs may be warranted. It is recommended that the injectable buprenorphine dose be halved for patients who receive other drugs with CNS depressant effects; for the buprenorphine transdermal patch, start with the 5 mcg/hour patch. Monitor patients for sedation or respiratory depression.
    Buprenorphine; Naloxone: (Major) Concomitant use of buprenorphine with other CNS depressants can lead to additive CNS depressive effects. Hypotension, profound sedation, coma, respiratory depression, or death may occur. Prior to concurrent use of buprenorphine in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. A dose reduction of one or both drugs may be warranted. It is recommended that the injectable buprenorphine dose be halved for patients who receive other drugs with CNS depressant effects; for the buprenorphine transdermal patch, start with the 5 mcg/hour patch. Monitor patients for sedation or respiratory depression. (Major) Naloxone reverses the analgesic and adverse effects of opiate agonists and mixed opiate agonists/antagonists (e.g., buprenorphine, butorphanol, nalbuphine, and pentazocine). Reversal of respiratory depression by partial agonists or mixed agonist/antagonists may be incomplete or require higher doses of naloxone. For example, large doses of naloxone are required to antagonize buprenorphine. Buprenorphine antagonism is characterized by a gradual onset of the reversal effects and a decreased duration of action of the normally prolonged respiratory depression. Respirations should be mechanically assisted as clinically indicated. Patients with severe pain or patients who are physically dependent on opiate analgesics can experience severe pain or withdrawal symptoms, respectively. Methohexital appears to block the acute onset of withdrawal symptoms induced by naloxone in opiate addicts. Clinicians should be prepared to manage possible reactions after naloxone administration.
    Bupropion: (Moderate) Plasma concentrations of opiate agents metabolized by CYP2D6, such as pentazocine, may be increased if bupropion, an inhibitor of the CYP2D6 isoenzyme, is added. Dosage reductions of pentazocine may be needed. Conversely, if bupropion therapy is discontinued, dosages of pentazocine may need to be adjusted upward in some patients.
    Bupropion; Naltrexone: (Major) When naltrexone is used as adjuvant treatment of opiate or alcohol dependence, use is contraindicated in patients currently receiving mixed opiate agonists/antagonists. Naltrexone will antagonize the therapeutic benefits of mixed opiate agonists/antagonists and will induce a withdrawal reaction in patients with physical dependence to opioids. Also, patients should be opiate-free for at least 7 to 10 days prior to initiating naltrexone therapy. If there is any question of opioid use in the past 7-10 days and the patient is not experiencing opioid withdrawal symptoms and/or the urine is negative for opioids, a naloxone challenge test needs to be performed. If a patient receives naltrexone and an opiate agonist is needed for an emergency situation, large doses of opiate agonists may ultimately overwhelm naltrexone antagonism of opiate receptors. Immediately following administration of exogenous opiate agonists, the opiate plasma concentration may be sufficient to overcome naltrexone competitive blockade, but the patient may experience deeper and more prolonged respiratory depression and thus, may be in danger of respiratory arrest and circulatory collapse. Non-receptor mediated actions like facial swelling, itching, generalized erythema, or bronchoconstriction may occur presumably due to histamine release. A rapidly acting opiate agonist is preferred as the duration of respiratory depression will be shorter. Patients receiving naltrexone may also experience opiate side effects (respiratory insufficiency or arrest or circulatory collapse) with low doses of opiate agonists. If the opiate agonist is taken in such a way that high concentrations remain in the body beyond the time naltrexone exerts its therapeutic effects, serious side effects may occur. (Moderate) Plasma concentrations of opiate agents metabolized by CYP2D6, such as pentazocine, may be increased if bupropion, an inhibitor of the CYP2D6 isoenzyme, is added. Dosage reductions of pentazocine may be needed. Conversely, if bupropion therapy is discontinued, dosages of pentazocine may need to be adjusted upward in some patients.
    Buspirone: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include buspirone.
    Butabarbital: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Butorphanol: (Major) Concomitant use of butorphanol and pentazocine can potentiate respiratory depression, CNS depression (e.g., dizziness, impaired mental function), and sedation. If these drugs need to be administered together, use the smallest effective dose and the longest dosing frequency of butorphanol.
    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.
    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.
    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.
    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.
    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.
    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.
    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.
    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.
    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.
    Carbidopa; Levodopa; Entacapone: (Moderate) Concomitant use of opiate agonists-antagonists with other central nervous system (CNS) depressants, such as COMT inhibitors, can potentiate the effects of the opiate agonists-antagonist and may lead to additive CNS or respiratory depression. Prior to concurrent use of a mixed opiate agonist-antagonist in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. If these agents are used together, reduced dosages may be necessary. Carefully monitor the patient for hypotension, CNS depression, and respiratory depression.
    Carbinoxamine; Hydrocodone; Phenylephrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Carbinoxamine; Hydrocodone; Pseudoephedrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Cariprazine: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Cetirizine: (Moderate) Additive drowsiness may occur if cetirizine or levocetirizine is administered with other drugs that depress the CNS. Cetirizine or levocetirizine should be used with caution with pentazocine.
    Cetirizine; Pseudoephedrine: (Moderate) Additive drowsiness may occur if cetirizine or levocetirizine is administered with other drugs that depress the CNS. Cetirizine or levocetirizine should be used with caution with pentazocine.
    Chlordiazepoxide: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Chlordiazepoxide; Clidinium: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation. (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.
    Chlorpheniramine; Codeine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as codeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of mu-receptor opiate agonists and reduce analgesic effects of codeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as dihydrocodeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce the analgesic effects of dihydrocodeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Chlorpheniramine; Dihydrocodeine; Pseudoephedrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as dihydrocodeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce the analgesic effects of dihydrocodeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Chlorpheniramine; Guaifenesin; Hydrocodone; Pseudoephedrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Chlorpheniramine; Hydrocodone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Chlorpheniramine; Hydrocodone; Phenylephrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Chlorpheniramine; Hydrocodone; Pseudoephedrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Chlorpromazine: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as phenothiazines, can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously with phenothiazines.
    Clobazam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Clonazepam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Clorazepate: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Clozapine: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Codeine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as codeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of mu-receptor opiate agonists and reduce analgesic effects of codeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Codeine; Guaifenesin: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as codeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of mu-receptor opiate agonists and reduce analgesic effects of codeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Codeine; Phenylephrine; Promethazine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as codeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of mu-receptor opiate agonists and reduce analgesic effects of codeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist. (Moderate) Because promethazine causes pronounced sedation, an enhanced CNS depressant effect or additive drowsiness may occur when it is combined with other CNS depressants including pentazocine. Respiratory depressant agents in combination with promethazine should be avoided in children and administered in reduced dosage with close monitoring to other patients receiving promethazine.
    Codeine; Promethazine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as codeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of mu-receptor opiate agonists and reduce analgesic effects of codeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist. (Moderate) Because promethazine causes pronounced sedation, an enhanced CNS depressant effect or additive drowsiness may occur when it is combined with other CNS depressants including pentazocine. Respiratory depressant agents in combination with promethazine should be avoided in children and administered in reduced dosage with close monitoring to other patients receiving promethazine.
    COMT inhibitors: (Moderate) Concomitant use of opiate agonists-antagonists with other central nervous system (CNS) depressants, such as COMT inhibitors, can potentiate the effects of the opiate agonists-antagonist and may lead to additive CNS or respiratory depression. Prior to concurrent use of a mixed opiate agonist-antagonist in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. If these agents are used together, reduced dosages may be necessary. Carefully monitor the patient for hypotension, CNS depression, and respiratory depression.
    Darifenacin: (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.
    Deutetrabenazine: (Major) Concomitant use of mixed opiate agonists/antagonists with deutetrabenazine may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with deutetrabenazine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking deutetrabenazine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If deutetrabenazine is prescribed for a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of deutetrabenazine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Dextromethorphan; Promethazine: (Moderate) Because promethazine causes pronounced sedation, an enhanced CNS depressant effect or additive drowsiness may occur when it is combined with other CNS depressants including pentazocine. Respiratory depressant agents in combination with promethazine should be avoided in children and administered in reduced dosage with close monitoring to other patients receiving promethazine.
    Diazepam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If parental diazepam is used with a mixed opiate agonist/antagonist, reduce the mixed opiate agonist/antagonist dosage by at least 1/3. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Dicyclomine: (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.
    Dihydrocodeine; Guaifenesin; Pseudoephedrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as dihydrocodeine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce the analgesic effects of dihydrocodeine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Diphenhydramine; Hydrocodone; Phenylephrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Disopyramide: (Moderate) Use pentazocine with caution in any patient receiving medication with anticholinergic activity. Coadministration of pentazocine with disopyramide may result in additive anticholinergic effects, such as urinary retention and constipation.
    Dronabinol, THC: (Moderate) Concomitant use of dronabinol with other CNS depressants, such as pentazocine, can potentiate the effects of dronabinol on respiratory depression.
    Droperidol: (Major) Mixed opiate agonists/antagonists have additive or potentiating effects with droperidol. Following administration of droperidol, lower doses of the other CNS depressant should be used.
    Entacapone: (Moderate) Concomitant use of opiate agonists-antagonists with other central nervous system (CNS) depressants, such as COMT inhibitors, can potentiate the effects of the opiate agonists-antagonist and may lead to additive CNS or respiratory depression. Prior to concurrent use of a mixed opiate agonist-antagonist in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. If these agents are used together, reduced dosages may be necessary. Carefully monitor the patient for hypotension, CNS depression, and respiratory depression.
    Estazolam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Eszopiclone: (Moderate) Concomitant use of pentazocine with eszopiclone can potentiate respiratory depression, CNS depression, and sedation. In addition, the risk of next-day psychomotor impairment is increased during co-administration, which may decrease the ability to perform tasks requiring full mental alertness such as driving. Pentazocine should be used cautiously in any patient receiving eszopiclone. If concurrent use is necessary, a dose reduction of one or both medications may be required.
    Ethanol: (Major) Alcohol is associated with CNS depression. The combined use of alcohol and CNS depressants can lead to additive CNS depression, which could be dangerous in tasks requiring mental alertness and fatal in overdose. Alcohol taken with other CNS depressants can lead to additive respiratory depression, hypotension, profound sedation, or coma. Consider the patient's use of alcohol or illicit drugs when prescribing CNS depressant medications. In many cases, the patient should receive a lower dose of the CNS depressant initially if the patient is not likely to be compliant with avoiding alcohol.
    Ezogabine: (Moderate) Due to the CNS effects of ezogabine, an enhanced CNS depressant effect may occur during concurrent use of other centrally-acting medications such as pentazocine. Patients should be monitored for excessive somnolence during concurrent therapy with this agent.
    Fentanyl: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as fentanyl. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Fesoterodine: (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.
    Flavoxate: (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.
    Flibanserin: (Moderate) The concomitant use of flibanserin with CNS depressants, such as mixed opiate agonists/antagonists or their combinations (e.g., buprenorphine; naloxone), may increase the risk of CNS depression (e.g., dizziness, somnolence) compared to the use of flibanserin alone. Patients should avoid activities requiring full alertness (e.g., operating machinery or driving) until at least 6 hours after each dose and until they know how flibanserin affects them.
    Fluoxetine; Olanzapine: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Fluphenazine: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as phenothiazines, can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously with phenothiazines.
    Flurazepam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Glycopyrrolate: (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.
    Glycopyrrolate; Formoterol: (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.
    Guaifenesin; Hydrocodone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Guaifenesin; Hydrocodone; Pseudoephedrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Haloperidol: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include haloperidol.
    Homatropine; Hydrocodone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist. (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.
    Hydrocodone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Hydrocodone; Ibuprofen: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Hydrocodone; Phenylephrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Hydrocodone; Potassium Guaiacolsulfonate: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Hydrocodone; Potassium Guaiacolsulfonate; Pseudoephedrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Hydrocodone; Pseudoephedrine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydrocodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of hydrocodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Hydromorphone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as hydromorphone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Hyoscyamine: (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.
    Hyoscyamine; Methenamine; Methylene Blue; Phenyl Salicylate; Sodium Biphosphate: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when pentazocine is used concomitantly with an anticholinergic drug. The concomitant use of pentazocine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) Theoretically, concurrent use of methylene blue and pentazocine may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and pentazocine increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Ibuprofen; Oxycodone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as oxycodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of oxycodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Iloperidone: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Indacaterol; Glycopyrrolate: (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.
    Levocetirizine: (Moderate) Additive drowsiness may occur if cetirizine or levocetirizine is administered with other drugs that depress the CNS. Cetirizine or levocetirizine should be used with caution with pentazocine.
    Levomethadyl: (Major) Pentazocine may partially block the analgesic, respiratory depressant and CNS depressant effects of pure opiate agonists. Due to their antagonistic properties, pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists.
    Levorphanol: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as levorphanol. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Linezolid: (Moderate) Patients receiving concurrent pentazocine and agents with monoamine oxidase inhibitor (MAOI) activity, such as linezolid may be at increased risk for developing serotonin syndrome. Serious CNS reactions, such as serotonin syndrome, have been reported during the concurrent use of linezolid and psychiatric medications that enhance central serotonergic activity; therefore, caution is warranted with concomitant use of other agents with serotonergic activity, including pentazocine. If concurrent use is clinically indicated, the patient needs to be carefully observed for any signs or symptoms of serotonin excess such as restlessness, myoclonus, confusion, hyperreflexia, diaphoresis, shivering, tachycardia, and tremor.
    Lorazepam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Lurasidone: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Magnesium Salts: (Minor) Because of the CNS-depressant effects of magnesium sulfate, additive central-depressant effects can occur following concurrent administration with CNS depressants such as opiate agonists/antagonists. Caution should be exercised when using these agents concurrently.
    Maprotiline: (Moderate) Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity. Coadministration of pentazocine with maprotiline may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation.
    Mepenzolate: (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.
    Meperidine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as meperidine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of meperidine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Meperidine; Promethazine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as meperidine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of meperidine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist. (Moderate) Because promethazine causes pronounced sedation, an enhanced CNS depressant effect or additive drowsiness may occur when it is combined with other CNS depressants including pentazocine. Respiratory depressant agents in combination with promethazine should be avoided in children and administered in reduced dosage with close monitoring to other patients receiving promethazine.
    Mephobarbital: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Meprobamate: (Moderate) Concomitant use of pentazocine with meprobamate can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously meprobamate. If concurrent use is necessary, a dose reduction of one or both medications may be required.
    Mesoridazine: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as phenothiazines, can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously with phenothiazines.
    Methadone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as methadone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Methenamine; Sodium Acid Phosphate; Methylene Blue; Hyoscyamine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when pentazocine is used concomitantly with an anticholinergic drug. The concomitant use of pentazocine and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. (Moderate) Theoretically, concurrent use of methylene blue and pentazocine may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and pentazocine increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Methocarbamol: (Moderate) Methocarbamol may cause additive CNS depression if used concomitantly with other CNS depressants. Dosage adjustments of either or both medications may be necessary.
    Methohexital: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Methscopolamine: (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.
    Methylene Blue: (Moderate) Theoretically, concurrent use of methylene blue and pentazocine may increase the risk of serotonin syndrome. Methylene blue is a thiazine dye that is also a potent, reversible inhibitor of the enzyme responsible for the catabolism of serotonin in the brain (MAO-A) and pentazocine increases central serotonin effects. Cases of serotonin syndrome have been reported, primarily following administration of standard infusions of methylene blue (1 to 8 mg/kg) as a visualizing agent in parathyroid surgery, in patients receiving selective serotonin reuptake inhibitors, serotonin/norepinephrine reuptake inhibitors, or clomipramine. It is not known if patients receiving other serotonergic psychiatric agents with intravenous methylene blue are at a comparable risk or if methylene blue administered by other routes (e.g., orally, local injection) or in doses less than 1 mg/kg IV can produce a similar outcome. Published interaction reports between intravenously administered methylene blue and serotonergic psychiatric agents have documented symptoms including lethargy, confusion, delirium, agitation, aggression, obtundation, myoclonus, expressive aphasia, hypertonia, pyrexia, elevated blood pressure, seizures, and/or coma. Serotonin syndrome is characterized by rapid development of various symptoms such as hyperthermia, hypertension, myoclonus, rigidity, hyperhidrosis, incoordination, diarrhea, mental status changes (e.g., confusion, delirium, or coma), and in rare cases, death.
    Midazolam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Minocycline: (Minor) Injectable minocycline contains magnesium sulfate heptahydrate. Because of the CNS-depressant effects of magnesium sulfate, additive central-depressant effects can occur following concurrent administration with CNS depressants such as pentazocine. Caution should be exercised when using these agents concurrently.
    Mirtazapine: (Major) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving mirtazapine.
    Molindone: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as molindone, can potentiate respiratory depression, CNS depression, and sedation.
    Monoamine oxidase inhibitors: (Major) Patients receiving concurrent pentazocine and MAOIs are at increased risk for developing serotonin syndrome; pentazocine should be used cautiously, if at all, in these patients.
    Morphine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as morphine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of morphine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Morphine; Naltrexone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as morphine. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of morphine. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Nabilone: (Moderate) Concomitant use of mixed opiate agonists-antagonists with nabilone can potentiate the effects of nabilone and may lead to additive CNS or respiratory depression. Prior to concurrent use of nabilone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. If these agents are used together, a reduced dosage nabilone and/or the opiate agonist-antagonist may be necessary. Carefully monitor the patient for hypotension, CNS depression, and respiratory depression.
    Nalbuphine: (Major) Concomitant use of pentazocine and nalbuphine can potentiate respiratory depression, CNS depression (e.g., dizziness, impaired mental function), and sedation. If these drugs are administered together, the dose of one or both drugs needs to be reduced.
    Nalmefene: (Major) Naloxone, nalmefene, and naltrexone act as opiate antagonists at all opiate receptors. Administration of an opiate antagonist will override the actions of mixed opiate agonist/antagonists and precipitate opioid withdrawal effects. While opiate antagonism may be desirable in a patient with respiratory depression caused by the mixed opiate agonist/antagonist, severe pain can be unmasked and opiate withdrawal symptoms may occur in patients who have received chronic opiate agonist therapy.
    Naloxone: (Major) Naloxone reverses the analgesic and adverse effects of opiate agonists and mixed opiate agonists/antagonists (e.g., buprenorphine, butorphanol, nalbuphine, and pentazocine). Reversal of respiratory depression by partial agonists or mixed agonist/antagonists may be incomplete or require higher doses of naloxone. For example, large doses of naloxone are required to antagonize buprenorphine. Buprenorphine antagonism is characterized by a gradual onset of the reversal effects and a decreased duration of action of the normally prolonged respiratory depression. Respirations should be mechanically assisted as clinically indicated. Patients with severe pain or patients who are physically dependent on opiate analgesics can experience severe pain or withdrawal symptoms, respectively. Methohexital appears to block the acute onset of withdrawal symptoms induced by naloxone in opiate addicts. Clinicians should be prepared to manage possible reactions after naloxone administration.
    Naltrexone: (Major) When naltrexone is used as adjuvant treatment of opiate or alcohol dependence, use is contraindicated in patients currently receiving mixed opiate agonists/antagonists. Naltrexone will antagonize the therapeutic benefits of mixed opiate agonists/antagonists and will induce a withdrawal reaction in patients with physical dependence to opioids. Also, patients should be opiate-free for at least 7 to 10 days prior to initiating naltrexone therapy. If there is any question of opioid use in the past 7-10 days and the patient is not experiencing opioid withdrawal symptoms and/or the urine is negative for opioids, a naloxone challenge test needs to be performed. If a patient receives naltrexone and an opiate agonist is needed for an emergency situation, large doses of opiate agonists may ultimately overwhelm naltrexone antagonism of opiate receptors. Immediately following administration of exogenous opiate agonists, the opiate plasma concentration may be sufficient to overcome naltrexone competitive blockade, but the patient may experience deeper and more prolonged respiratory depression and thus, may be in danger of respiratory arrest and circulatory collapse. Non-receptor mediated actions like facial swelling, itching, generalized erythema, or bronchoconstriction may occur presumably due to histamine release. A rapidly acting opiate agonist is preferred as the duration of respiratory depression will be shorter. Patients receiving naltrexone may also experience opiate side effects (respiratory insufficiency or arrest or circulatory collapse) with low doses of opiate agonists. If the opiate agonist is taken in such a way that high concentrations remain in the body beyond the time naltrexone exerts its therapeutic effects, serious side effects may occur.
    Nefazodone: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as nefazodone, can potentiate respiratory depression, CNS depression, and sedation.
    Olanzapine: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Oxazepam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Oxybutynin: (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.
    Oxycodone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as oxycodone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects of oxycodone. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Oxymorphone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as oxymorphone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Paliperidone: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Pentazocine; Naloxone: (Major) Naloxone reverses the analgesic and adverse effects of opiate agonists and mixed opiate agonists/antagonists (e.g., buprenorphine, butorphanol, nalbuphine, and pentazocine). Reversal of respiratory depression by partial agonists or mixed agonist/antagonists may be incomplete or require higher doses of naloxone. For example, large doses of naloxone are required to antagonize buprenorphine. Buprenorphine antagonism is characterized by a gradual onset of the reversal effects and a decreased duration of action of the normally prolonged respiratory depression. Respirations should be mechanically assisted as clinically indicated. Patients with severe pain or patients who are physically dependent on opiate analgesics can experience severe pain or withdrawal symptoms, respectively. Methohexital appears to block the acute onset of withdrawal symptoms induced by naloxone in opiate addicts. Clinicians should be prepared to manage possible reactions after naloxone administration.
    Pentobarbital: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Perphenazine: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as phenothiazines, can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously with phenothiazines.
    Perphenazine; Amitriptyline: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as phenothiazines, can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously with phenothiazines.
    Phenobarbital: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Phenothiazines: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as phenothiazines, can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously with phenothiazines.
    Phenylephrine; Promethazine: (Moderate) Because promethazine causes pronounced sedation, an enhanced CNS depressant effect or additive drowsiness may occur when it is combined with other CNS depressants including pentazocine. Respiratory depressant agents in combination with promethazine should be avoided in children and administered in reduced dosage with close monitoring to other patients receiving promethazine.
    Pimozide: (Moderate) Due to the effects of pimozide on cognition, it should be used cautiously with other CNS depressants including pentazocine.
    Pramipexole: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as pramipexole, can potentiate respiratory depression, CNS depression, and sedation.
    Pregabalin: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as pregabalin, can potentiate respiratory depression, CNS depression, and sedation.
    Primidone: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Procarbazine: (Major) Patients receiving concurrent pentazocine and MAOI inhbitors may be at increased risk for developing serotonin syndrome; pentazocine should be used cautiously in patients receiving other drugs with MAOI activity, such as procarbazine.
    Prochlorperazine: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as phenothiazines, can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously with phenothiazines.
    Promethazine: (Moderate) Because promethazine causes pronounced sedation, an enhanced CNS depressant effect or additive drowsiness may occur when it is combined with other CNS depressants including pentazocine. Respiratory depressant agents in combination with promethazine should be avoided in children and administered in reduced dosage with close monitoring to other patients receiving promethazine.
    Propantheline: (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.
    Propoxyphene: (Major) Pentazocine may partially block the analgesic, respiratory depressant and CNS depressant effects of pure opiate agonists. Due to their antagonistic properties, pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists.
    Quazepam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Quetiapine: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Rasagiline: (Major) The CNS-depressant effects of MAOIs can be potentiated with concomitant administration of other drugs known to cause CNS depression, such as pentazocine. Patients receiving concurrent pentazocine and monoamine oxidase inhibitors (MAOIs) may be at increased risk for developing serotonin syndrome. If concurrent use is clinically indicated, observe the patient for signs or symptoms of serotonin excess such as restlessness, myoclonus, confusion, hyperreflexia, diaphoresis, shivering, tachycardia, and tremor. Use cautiously with MAOIs; warn patients to not drive or perform other hazardous activities until they know how this drug combination affects them.
    Remifentanil: (Major) Concurrent use of pentazocine may reduce the analgesic effect of remifentanil and/or precipitate withdrawal symptoms. If coadministration is necessary, carefully observe the patient, especially during remifentanil initiation and dosage adjustment. Consider discontinuing remifentanil and instituting alternative analgesia if the patient is not responding appropriately. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Risperidone: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Rotigotine: (Moderate) Concomitant use of rotigotine with other CNS depressants, such as opiate agonists-antagonists, can potentiate the sedation effects of rotigotine.
    Scopolamine: (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.
    Secobarbital: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Sedating H1-blockers: (Moderate) Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity. Coadministration of pentazocine with sedating H1-blockers may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation.
    Selective serotonin reuptake inhibitors: (Major) Because of the potential risk and severity of serotonin syndrome or neuroleptic malignant syndrome-like reactions, caution should be observed when administering selective serotonin reuptake inhibitors (SSRIs) with other drugs that have serotonergic properties such as pentazocine. Serotonin syndrome is characterized by rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. Serotonin syndrome, in its most severe form, can resemble neuroleptic malignant syndrome. Patients receiving this combination should be monitored for the emergence of serotonin syndrome or neuroleptic malignant syndrome-like reactions
    Serotonin norepinephrine reuptake inhibitors: (Major) Because of the potential risk and severity of serotonin syndrome or neuroleptic malignant syndrome-like reactions, caution should be observed when administering serotonin norepinephrine reuptake inhibitors (SNRIs) with other drugs that have serotonergic properties such as pentazocine. Serotonin syndrome is characterized by rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. Serotonin syndrome, in its most severe form, can resemble neuroleptic malignant syndrome. Patients receiving this combination should be monitored for the emergence of serotonin syndrome or neuroleptic malignant syndrome-like reactions.
    Sibutramine: (Major) Sibutramine is a serotonin reuptake inhibitor. Serotonin syndrome has been reported or may be possible with the concomitant use of pentazocine. If such a combination is clinically indicated, appropriate observation of the patient is warranted.
    Skeletal Muscle Relaxants: (Moderate) Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity. Coadministration of pentazocine with skeletal muscle relaxants may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation.
    Solifenacin: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when pentazocine is used concomitantly with an anticholinergic drug, such as solifenacin. 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.
    Sufentanil: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as sufentanil. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Suvorexant: (Moderate) CNS depressant drugs may have cumulative effects when administered concurrently and they should be used cautiously with suvorexant. A reduction in dose of the CNS depressant may be needed. These agents include mixed opiate agonists/antagonists.
    Tapentadol: (Major) Avoid the concomitant use of tapentadol and opiate agonists/antagonists (e.g., buprenorphine, butorphanol, nalbuphine, or pentazocine). Opiate agonists/antagonists may partially block the analgesic, respiratory depressant, and CNS depressant effects of tapentadol. Due to their antagonistic properties, opiate agonists/antagonists may cause withdrawal symptoms in patients receiving chronic opiate agonists. These agents may also be used concurrently with some opiate agonists and cause additive CNS, respiratory, and hypotensive effects. Consider dose reduction of the opiate agonist in situations of concomitant prescription. The additive or antagonistic effects are dependent upon the dose of pure opiate agonist used; antagonistic effects are more common at low to moderate doses of the pure opiate agonist.
    Tedizolid: (Minor) Caution is warranted with the concurrent use of tedizolid and pentazocine. Tedizolid is an antibiotic that is also a weak reversible, non-selective inhibitor of MAO. Serious CNS reactions, such as serotonin syndrome, have been reported during the concurrent use of linezolid, which is structurally similar to tedizolid, and psychiatric medications that enhance central serotonergic activity; therefore, caution is warranted with concomitant use of other agents with serotonergic activity, including pentazocine.
    Temazepam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Tetrabenazine: (Moderate) Additive effects are possible when tetrabenazine is combined with other drugs that cause CNS depression, like pentazocine. Concurrent use of tetrabenazine and pentazocine can increase both the frequency and the intensity of adverse effects such as drowsiness, sedation, dizziness, and orthostatic hypotension.
    Thalidomide: (Major) Avoid the concomitant use of thalidomide with other central nervous system depressants such as pentazocine due to the potential for additive sedative effects.
    Thiethylperazine: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as phenothiazines, can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously with phenothiazines.
    Thiopental: (Moderate) Concomitant use of pentazocine with other CNS depressants can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving these agents, which may include barbiturates.
    Thioridazine: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as phenothiazines, can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously with phenothiazines.
    Thiothixene: (Moderate) Thiothixene can potentiate the CNS-depressant action of other drugs such as pentazocine. Caution should be exercised during simultaneous use of these agents due to potential excessive CNS effects or additive hypotension.
    Tizanidine: (Moderate) Concurrent use of tizanidine and CNS depressants like pentazocine can cause additive CNS depression.
    Tobacco: (Moderate) Tobacco smoking is associated with increased hepatic metabolism of pentazocine; reduced analgesia with pentazocine has been reported in cigarette smokers. Conversely, sudden smoking cessation may cause an increase in the therapeutic effects of pentazocine as hepatic enzyme activities return to normal, despite the use of nicotine replacement products.
    Tolcapone: (Moderate) Concomitant use of opiate agonists-antagonists with other central nervous system (CNS) depressants, such as COMT inhibitors, can potentiate the effects of the opiate agonists-antagonist and may lead to additive CNS or respiratory depression. Prior to concurrent use of a mixed opiate agonist-antagonist in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. If these agents are used together, reduced dosages may be necessary. Carefully monitor the patient for hypotension, CNS depression, and respiratory depression.
    Tolterodine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when pentazocine is used concomitantly with an anticholinergic drug, such as tolterodine. 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.
    Tramadol: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as tramadol. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. There is also a potential increased risk of seizures if tramadol and pentazocine are given concurrently. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
    Trazodone: (Moderate) Concomitant use of pentazocine with other CNS depressants such as trazodone can potentiate respiratory depression and/or sedation. The central nervous system (CNS) effects of pentazocine and other CNS depressants are additive. Trazodone has significant potential for sedation. In addition, both agents may increase serotonin activity, which may increase the risk for serotonin-related side effects and in rare cases lead to serotonin syndrome.
    Triazolam: (Major) Concomitant use of mixed opiate agonists/antagonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of mixed opiate agonists/antagonists with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If a mixed opiate agonist/antagonist is initiated in a patient taking a benzodiazepine, use a lower initial dose of the mixed opiate agonist/antagonist and titrate to clinical response. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking a mixed opiate agonist/antagonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
    Tricyclic antidepressants: (Moderate) Pain medications such as pentazocine should be combined cautiously with tricyclic antidepressants due to the possibility of additive CNS depression, respiratory depression, hypotension, or decreased intestinal motility. Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering tricyclic antidepressants with other drugs that have serotonergic properties such as pentazocine. Serotonin syndrome is characterized by rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. Serotonin syndrome, in its most severe form, can resemble neuroleptic malignant syndrome. If serotonin syndrome is suspected, tricyclic antidepressant and concurrent serotonergic agents should be discontinued.
    Trifluoperazine: (Moderate) Concomitant use of pentazocine with other CNS depressants, such as phenothiazines, can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously with phenothiazines.
    Trihexyphenidyl: (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.
    Trimethobenzamide: (Moderate) The concurrent use of trimethobenzamide with other medications that cause CNS depression, like pentazocine, may potentiate the effects of either trimethobenzamide or pentazocine.
    Trospium: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when pentazocine is used concomitantly with an anticholinergic drug, such as trospium. 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.
    Vigabatrin: (Moderate) Vigabatrin may cause somnolence and fatigue. Drugs that can cause CNS depression, if used concomitantly with vigabatrin, may increase both the frequency and the intensity of adverse effects such as drowsiness, sedation, and dizziness. Caution should be used when vigabatrin is given with pentazocine.
    Vilazodone: (Major) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering vilazodone with other drugs that have serotonergic properties such as pentazocine. Serotonin syndrome is characterized by the rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. Patients receiving vilazodone and pentazocine should be monitored for the emergence of serotonin syndrome, particularly during treatment initiation and during dosage increases. Vilazodone and pentazocine should be discontinued if serotonin syndrome occurs and supportive symptomatic treatment should be initiated. Due to the CNS effects of vilazodone, caution should be used when vilazodone is given in combination with other centrally acting medications such as pentazocine.
    Vortioxetine: (Major) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering vortioxetine with other drugs that have serotonergic properties such as pentazocine. Serotonin syndrome is characterized by rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. Serotonin syndrome, in its most severe form, can resemble neuroleptic malignant syndrome. If serotonin syndrome is suspected, vortioxetine and concurrent serotonergic agents should be discontinued.
    Zaleplon: (Moderate) Concomitant use of pentazocine with zaleplon can potentiate respiratory depression, CNS depression, and sedation. Pentazocine should be used cautiously in any patient receiving zaleplon. If concurrent use is necessary, a dose reduction of one or both medications may be required.
    Ziconotide: (Moderate) Concurrent use of ziconotide and opiate agonists-antagonists may result in an increased incidence of dizziness and confusion. Ziconotide neither interacts with opiate receptors nor potentiates opiate-induced respiratory depression. However, in animal models, ziconotide did potentiate gastrointestinal motility reduction by opioid agonists.
    Ziprasidone: (Moderate) Coadministration of pentazocine with atypical antipsychotics may result in additive respiratory and CNS depression and anticholinergic effects, such as urinary retention and constipation. Use pentazocine with caution in any patient receiving medication with CNS depressant and/or anticholinergic activity.
    Zolpidem: (Moderate) Concomitant use of pentazocine with zolpidem can potentiate respiratory depression, CNS depression, and sedation. In addition, sleep-related behaviors, such as sleep-driving, are more likely to occur during concurrent use of zolpidem and other CNS depressants than with zolpidem alone. Pentazocine should be used cautiously in any patient receiving zolpidem. If concurrent use is necessary, a dose reduction of one or both medications may be required. For Intermezzo brand of sublingual zolpidem tablets, reduce the dose to 1.75 mg/night.

    PREGNANCY AND LACTATION

    Pregnancy

    According to the manufacturer, pentazocine is excreted in human milk and cautious use is advised in women who are breast-feeding. Alternative analgesics that are considered to be usually compatible with breast-feeding by the American Academy of Pediatrics (AAP) include acetaminophen, ibuprofen, indomethacin, naproxen, piroxicam, and morphine. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally ingested drug, healthcare providers are encouraged to report the adverse effect to the FDA.

    MECHANISM OF ACTION

    Pentazocine is a mixed agonist-antagonist at opiate receptors. Only the l-isomer of pentazocine has analgesic activity; the d-isomer has little affinity for opiate receptors. Opiates are believed to exert their analgesic effects by stimulating specific opiate receptors, designated as mu, kappa, and delta, which have been reclassified by an International Union of Pharmacology subcommittee as OP1 (delta), OP2 (kappa), and OP3 (mu). Mu-receptors are considered the classic morphine-receptor type, and stimulation at this receptor produces supraspinal analgesia, respiratory depression, euphoria, and physical dependence. Pentazocine is an agonist at kappa-receptors but is a weak antagonist or partial agonist at mu-receptors. Actions at kappa-receptors are believed to produce alterations in the perception of pain, as well as the emotional response to pain. Pentazocine's antagonism at the mu-receptor is weaker than both butorphanol and nalbuphine. Pentazocine may have some agonistic effects at the mu-receptor, due to the morphine-like euphoria seen after therapeutic doses. It does not antagonize the respiratory depressive effects of morphine. However, when given to patients physically dependent on pure opiate agonists, pentazocine will decrease analgesia and may precipitate a withdrawal reaction. Since pentazocine is less active at the mu-receptor, it produces less respiratory depression and may pose a lower risk of physical dependence than morphine. Pentazocine has little effect on bile duct flow and duodenal smooth muscle activity. The dysphoric and psychotomimetic effects of pentazocine are due to activity at sigma opiate receptors. Cardiovascular responses to pentazocine are different from other opiates. Therapeutic doses generally cause an increase in blood pressure and heart rate. Therefore, pentazocine is not recommended for pain due to acute myocardial infarction, since it may simultaneously increase pulmonary arterial and central venous pressure, and thus, increase cardiac workload.
     
    The pharmacologic effects observed after opiates bind to their receptors might involve a second messenger such as cyclic AMP, which is synthesized by adenylate cyclase. Opioid receptors are coupled to these second messenger systems through an inhibitory G-protein (guanine nucleotide-binding protein). G-proteins are located at the cell surface along with many other receptors, including opioid receptors. G-proteins are thought to interact with opiate receptors, giving the receptor a higher affinity for the opiate. Binding of the opiate stimulates the exchange of guanosine triphosphate (GTP) for guanosine diphosphate (GDP) on the G-protein complex. Binding of GTP leads to a release of the G-protein subunit, which acts on the effector system. In this case, the effector system is adenylate cyclase and cyclic AMP located at the inner surface of the plasma membrane. Opioid agonists effectively inhibit adenylate cyclase and cause a decrease in intracellular cyclic AMP levels. Other research has shown that mu-, delta-, and kappa-receptors are associated with ion channels and control the influx of cations into the cell. Mu- and delta-receptor stimulation is associated with increasing potassium influx, and kappa-receptor activity is associated with reducing calcium influx in cells located in various human and animal nerve systems. All of these effects appear to ultimately reduce transmitter release, and may also be mediated through G-proteins.

    PHARMACOKINETICS

    Pentazocine is given parenterally via intravenous (IV), intramuscular (IM), or subcutaneous (SC) injection.
    Pentazocine is distributed into fetal circulation. It undergoes hepatic metabolism via oxidation and glucuronidation. A small amount of unchanged pentazocine and its metabolites are excreted in the urine. Data suggest that pentazocine is recirculated through the biliary system. The elimination half-life was measured as 3.6 hours (range 1.5 to 10 hours) in 24 healthy volunteers. Approximately 60% of the total dose is eliminated within 24 hours.

    Intravenous Route

    Following IV injection of pentazocine, the onset of analgesia is 2—3 minutes. The duration of analgesia is 2—3 hours.

    Intramuscular Route

    Following IM injection of pentazocine, the onset of analgesia is 15—20 minutes. The duration of analgesia is 2—3 hours.

    Subcutaneous Route

    Following SC injection of pentazocine, the onset of analgesia is 15—20 minutes.