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Pentazocine

Medically reviewed by Drugs.com. Last updated on Oct 11, 2020.

Pronunciation

(pen TAZ oh seen)

Index Terms

  • Pentazocine Lactate

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Solution, Injection:

Talwin: 30 mg/mL (1 mL [DSC])

Talwin: 30 mg/mL (10 mL [DSC]) [contains methylparaben, sodium bisulfite]

Brand Names: U.S.

  • Talwin [DSC]

Pharmacologic Category

  • Analgesic, Opioid
  • Analgesic, Opioid Partial Agonist

Pharmacology

Agonist of kappa opiate receptors and partial agonist of mu opiate receptors in the CNS, causing inhibition of ascending pain pathways, altering the perception of and response to pain; produces analgesia, respiratory depression and sedation similar to opioids

Absorption

Oral [Canadian product]: Well absorbed; bioavailability is low due to extensive first-pass effect

Distribution

Children 4 to 8 years (mean ± SD): Vdss: 4 ± 1.2 L/kg (Hanunen 1993)

Metabolism

Hepatic via oxidative and glucuronide conjugation pathways; extensive first-pass effect

Excretion

Urine (small amounts as unchanged drug)

Onset of Action

IM, SubQ: 15 to 20 minutes; IV: 2 to 3 minutes; Oral [Canadian product]: 15 to 30 minutes

Time to Peak

Oral [Canadian product]: 1 to 3 hours

Duration of Action

Injection: 2 to 3 hours; Oral [Canadian product]: ≥3 hours

Half-Life Elimination

Prolonged with hepatic impairment

Neonates: 8 to 12 hours (estimated; Osifo 2008)

Children 4 to 8 years (mean ± SD): 3 ± 1.5 hours (Hanunen 1993)

Adults: 2 to 5 hours (Talwin Canadian product labeling)

Protein Binding

60%

Special Populations: Elderly

Longer mean elimination half-life, lower mean total plasma Cl, and a larger mean AUC.

Use: Labeled Indications

Injection:

Anesthesia: Sedative prior to surgery; supplement to surgical anesthesia.

Pain management: Management of pain severe enough to require an opioid analgesic and for which alternative treatments are inadequate.

Oral [Canadian product]: Pain management: Management of chronic or acute pain of moderate to severe degree.

Limitations of use: Reserve pentazocine for use in patients for whom alternative treatment options (eg, nonopioid analgesics, opioid combination products) are ineffective, not tolerated, or would be otherwise inadequate to provide sufficient management of pain.

Contraindications

Hypersensitivity (eg, anaphylaxis) to pentazocine or any component of the formulation; significant respiratory depression; acute or severe bronchial asthma in an unmonitored setting or in the absence of resuscitative equipment; GI obstruction, including paralytic ileus (known or suspected).

Canadian labeling: Additional contraindications (not in US labeling): Hypersensitivity to other opioids; suspected surgical abdomen (eg, acute appendicitis, pancreatitis); mild pain that can be managed with other pain medications; chronic obstructive airway; status asthmaticus; hypercapnia; cor pulmonale; acute alcoholism, delirium tremens, convulsive disorders; severe CNS depression, increased cerebrospinal or intracranial pressure, and head injury; concomitant use or use within 14 days of monoamine oxidase (MAO) inhibitors; pregnancy (oral); breastfeeding (oral)

Documentation of allergenic cross-reactivity for opioids is limited. However, because of similarities in chemical structure and/or pharmacologic actions, the possibility of cross-sensitivity cannot be ruled out with certainty.

Dosing: Adult

Note: Pentazocine injection has been discontinued in the United States for more than 1 year.

Injection:

Anesthesia, pain management:

IM, SubQ: 30 mg every 3 to 4 hours; do not exceed 60 mg/dose (maximum: 360 mg/day)

IV: 30 mg every 3 to 4 hours; do not exceed 30 mg/dose (maximum: 360 mg/day)

Labor pain:

IM: 30 mg once

IV: 20 mg every 2 to 3 hours as needed (maximum total dose: 60 mg)

Oral [Canadian product]: Pain management:

Not receiving opioids at time of initiation: Initial: 50 mg every 4 hours; titrate per response and tolerability to 50 to 100 mg every 3 to 4 hours. Maximum dose: 600 mg/day.

Receiving opioids at time of initiation: Refer to manufacturer's labeling for detailed dosing conversion.

Discontinuation of therapy: When discontinuing chronic opioid therapy, the dose should be gradually tapered down. An optimal universal tapering schedule for all patients has not been established (CDC [Dowell 2016]). Proposed schedules range from slow (eg, 10% reductions per week) to rapid (eg, 25% to 50% reduction every few days) (CDC 2015). Tapering schedules should be individualized to minimize opioid withdrawal while considering patient-specific goals and concerns as well as the pharmacokinetics of the opioid being tapered. An even slower taper may be appropriate in patients who have been receiving opioids for a long duration (eg, years), particularly in the final stage of tapering, whereas more rapid tapers may be appropriate in patients experiencing severe adverse events (CDC [Dowell 2016]). Monitor carefully for signs/symptoms of withdrawal. If the patient displays withdrawal symptoms, consider slowing the taper schedule; alterations may include increasing the interval between dose reductions, decreasing amount of daily dose reduction, pausing the taper and restarting when the patient is ready, and/or coadministration of an alpha-2 agonist (eg, clonidine) to blunt withdrawal symptoms (Berna 2015; CDC [Dowell 2016]). Continue to offer nonopioid analgesics as needed for pain management during the taper; consider nonopioid adjunctive treatments for withdrawal symptoms (eg, GI complaints, muscle spasm) as needed (Berna 2015; Sevarino 2018).

Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.

Dosing: Geriatric

Use with caution; may be more sensitive to analgesic and sedative effects; decrease initial dose and monitor closely

Dosing: Pediatric

Note: Pentazocine injection has been discontinued in the United States for more than 1 year.

Analgesia, perioperative: Limited data available: Children 5 to 9 years: IV: Initial: 0.5 mg/kg/dose administered with induction medication; small incremental doses may be repeated every 30 to 45 minutes as needed if procedure is prolonged; maximum total dose: 1.5 mg/kg/procedure. Dosing based on a study of pediatric patients (n=50) undergoing surgery (Ray 1994).

Analgesia, postoperative: Limited data available (APS 2016; Waterworth 1974):

Children 5 to 8 years: IM: 15 mg as a single dose

Children ≥9 years and Adolescents <15 years: IM: 30 mg as a single dose

Sedation, preoperative: Children and Adolescents ≤16 years: IM: 0.5 mg/kg/dose as a single dose; clinical trials suggest higher doses (0.8 to 1.9 mg/kg/dose) may provide a smoother induction (Nakagawa 2017; Rita 1970; Rita 1980). Note: Usual adult dose: 30 mg/dose.

Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.

Administration

Injection: For IM, IV, or SubQ use. Rotate injection sites for IM administration (eg, the upper outer quadrants of the buttocks, mid-lateral aspects of the thighs, and the deltoid areas); avoid intra-arterial injection; avoid SubQ use unless absolutely necessary (may cause tissue damage).

Oral: Tablet [Canadian product]: For oral use only. Administer after meals. Swallow whole; tablets should not be crushed, chewed, broken or dissolved.

Storage

Injection: Store at 20°C to 25°C (68°F to 77°F).

Tablets [Canadian product]: Store at 15°C to 30°C (59°F to 86°F).

Drug Interactions

Alizapride: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Alvimopan: Opioid Agonists may enhance the adverse/toxic effect of Alvimopan. This is most notable for patients receiving long-term (i.e., more than 7 days) opiates prior to alvimopan initiation. Management: Alvimopan is contraindicated in patients receiving therapeutic doses of opioids for more than 7 consecutive days immediately prior to alvimopan initiation. Consider therapy modification

Amphetamines: May enhance the analgesic effect of Opioid Agonists. Monitor therapy

Anticholinergic Agents: May enhance the adverse/toxic effect of Opioid Agonists. Specifically, the risk for constipation and urinary retention may be increased with this combination. Monitor therapy

Azelastine (Nasal): May enhance the CNS depressant effect of CNS Depressants. Avoid combination

Blonanserin: CNS Depressants may enhance the CNS depressant effect of Blonanserin. Management: Use caution if coadministering blonanserin and CNS depressants; dose reduction of the other CNS depressant may be required. Strong CNS depressants should not be coadministered with blonanserin. Consider therapy modification

Brimonidine (Topical): May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Bromopride: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Bromperidol: May enhance the CNS depressant effect of CNS Depressants. Avoid combination

Buprenorphine: Opioids (Mixed Agonist / Antagonist) may diminish the therapeutic effect of Buprenorphine. This combination may also induce opioid withdrawal. Avoid combination

Cannabidiol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Cannabis: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Chlormethiazole: May enhance the CNS depressant effect of CNS Depressants. Management: Monitor closely for evidence of excessive CNS depression. The chlormethiazole labeling states that an appropriately reduced dose should be used if such a combination must be used. Consider therapy modification

Chlorphenesin Carbamate: May enhance the adverse/toxic effect of CNS Depressants. Monitor therapy

CNS Depressants: May enhance the CNS depressant effect of Opioid Agonists. Management: Avoid concomitant use of opioid agonists and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Consider therapy modification

Desmopressin: Opioid Agonists may enhance the adverse/toxic effect of Desmopressin. Monitor therapy

Dimethindene (Topical): May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Diuretics: Opioid Agonists may enhance the adverse/toxic effect of Diuretics. Opioid Agonists may diminish the therapeutic effect of Diuretics. Monitor therapy

Dronabinol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Droperidol: May enhance the CNS depressant effect of CNS Depressants. Management: Consider dose reductions of droperidol or of other CNS agents (eg, opioids, barbiturates) with concomitant use. Consider therapy modification

Eluxadoline: Opioid Agonists may enhance the constipating effect of Eluxadoline. Avoid combination

Flunitrazepam: CNS Depressants may enhance the CNS depressant effect of Flunitrazepam. Management: Reduce the dose of CNS depressants when combined with flunitrazepam and monitor patients for evidence of CNS depression (eg, sedation, respiratory depression). Use non-CNS depressant alternatives when available. Consider therapy modification

Gastrointestinal Agents (Prokinetic): Opioid Agonists may diminish the therapeutic effect of Gastrointestinal Agents (Prokinetic). Monitor therapy

Kava Kava: May enhance the adverse/toxic effect of CNS Depressants. Monitor therapy

Lemborexant: May enhance the CNS depressant effect of CNS Depressants. Management: Dosage adjustments of lemborexant and of concomitant CNS depressants may be necessary when administered together because of potentially additive CNS depressant effects. Close monitoring for CNS depressant effects is necessary. Consider therapy modification

Lisuride: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Lofexidine: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Magnesium Sulfate: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Methotrimeprazine: CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Methotrimeprazine may enhance the CNS depressant effect of CNS Depressants. Management: Reduce the usual dose of CNS depressants by 50% if starting methotrimeprazine until the dose of methotrimeprazine is stable. Monitor patient closely for evidence of CNS depression. Consider therapy modification

Metoclopramide: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

MetyroSINE: CNS Depressants may enhance the sedative effect of MetyroSINE. Monitor therapy

Minocycline (Systemic): May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Monoamine Oxidase Inhibitors: Opioid Agonists may enhance the serotonergic effect of Monoamine Oxidase Inhibitors. This could result in serotonin syndrome. Management: Monitor for signs and symptoms of serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability, mental status changes) when these agents are combined. Monitor therapy

Nabilone: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Nalmefene: May diminish the therapeutic effect of Opioid Agonists. Management: Avoid the concomitant use of nalmefene and opioid agonists. Discontinue nalmefene 1 week prior to any anticipated use of opioid agonistss. If combined, larger doses of opioid agonists will likely be required. Consider therapy modification

Naltrexone: May diminish the therapeutic effect of Opioid Agonists. Management: Seek therapeutic alternatives to opioids. See full drug interaction monograph for detailed recommendations. Avoid combination

Opioid Agonists: Opioids (Mixed Agonist / Antagonist) may diminish the analgesic effect of Opioid Agonists. Management: Seek alternatives to mixed agonist/antagonist opioids in patients receiving pure opioid agonists, and monitor for symptoms of therapeutic failure/high dose requirements (or withdrawal in opioid-dependent patients) if patients receive these combinations. Avoid combination

Orphenadrine: CNS Depressants may enhance the CNS depressant effect of Orphenadrine. Avoid combination

Oxomemazine: May enhance the CNS depressant effect of CNS Depressants. Avoid combination

Oxybate Salt Products: CNS Depressants may enhance the CNS depressant effect of Oxybate Salt Products. Management: Consider alternatives to this combination when possible. If combined, dose reduction or discontinuation of one or more CNS depressants (including the oxybate salt product) should be considered. Interrupt oxybate salt treatment during short-term opioid use Consider therapy modification

Paraldehyde: CNS Depressants may enhance the CNS depressant effect of Paraldehyde. Avoid combination

Pegvisomant: Opioid Agonists may diminish the therapeutic effect of Pegvisomant. Monitor therapy

Perampanel: May enhance the CNS depressant effect of CNS Depressants. Management: Patients taking perampanel with any other drug that has CNS depressant activities should avoid complex and high-risk activities, particularly those such as driving that require alertness and coordination, until they have experience using the combination. Consider therapy modification

Piribedil: CNS Depressants may enhance the CNS depressant effect of Piribedil. Monitor therapy

Pramipexole: CNS Depressants may enhance the sedative effect of Pramipexole. Monitor therapy

Ramosetron: Opioid Agonists may enhance the constipating effect of Ramosetron. Monitor therapy

ROPINIRole: CNS Depressants may enhance the sedative effect of ROPINIRole. Monitor therapy

Rotigotine: CNS Depressants may enhance the sedative effect of Rotigotine. Monitor therapy

Rufinamide: May enhance the adverse/toxic effect of CNS Depressants. Specifically, sleepiness and dizziness may be enhanced. Monitor therapy

Serotonergic Agents (High Risk): Opioid Agonists may enhance the serotonergic effect of Serotonergic Agents (High Risk). This could result in serotonin syndrome. Management: Monitor for signs and symptoms of serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability, mental status changes) when these agents are combined. Monitor therapy

Sincalide: Drugs that Affect Gallbladder Function may diminish the therapeutic effect of Sincalide. Management: Consider discontinuing drugs that may affect gallbladder motility prior to the use of sincalide to stimulate gallbladder contraction. Consider therapy modification

Succinylcholine: May enhance the bradycardic effect of Opioid Agonists. Monitor therapy

Suvorexant: CNS Depressants may enhance the CNS depressant effect of Suvorexant. Management: Dose reduction of suvorexant and/or any other CNS depressant may be necessary. Use of suvorexant with alcohol is not recommended, and the use of suvorexant with any other drug to treat insomnia is not recommended. Consider therapy modification

Tetrahydrocannabinol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Tetrahydrocannabinol and Cannabidiol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Thalidomide: CNS Depressants may enhance the CNS depressant effect of Thalidomide. Avoid combination

Tobacco (Smoked): May decrease the serum concentration of Pentazocine. Monitor therapy

Zolpidem: CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: Reduce the Intermezzo brand sublingual zolpidem adult dose to 1.75 mg for men who are also receiving other CNS depressants. No such dose change is recommended for women. Avoid use with other CNS depressants at bedtime; avoid use with alcohol. Consider therapy modification

Adverse Reactions

The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.

Frequency not defined.

Cardiovascular: Circulatory depression, facial edema, flushing, hypertension, hypotension, increased peripheral vascular resistance, shock, syncope, tachycardia

Central nervous system: Central nervous system depression, chills, confusion, disorientation, dizziness, drowsiness, drug dependence (physical and psychological), euphoria, excitement, hallucination, headache, insomnia, irritability, malaise, nightmares, paresthesia, sedation

Dermatologic: Dermatitis, diaphoresis, erythema multiforme, pruritus, skin rash, Stevens-Johnson syndrome, toxic epidermal necrolysis, urticaria

Gastrointestinal: Abdominal distress, anorexia, constipation, diarrhea, dysgeusia, nausea, vomiting, xerostomia

Genitourinary: Urinary retention

Hematologic & oncologic: Agranulocytosis (rare), decreased white blood cell count, eosinophilia

Hypersensitivity: Anaphylaxis

Local: Injection site reaction (tissue damage and irritation)

Neuromuscular & skeletal: Tremor, weakness

Ophthalmic: Blurred vision, diplopia, miosis, nystagmus

Otic: Tinnitus

Respiratory: Dyspnea, respiratory depression (rare)

Postmarketing and/or case reports: Hypogonadism (Brennan, 2013; Debono, 2011)

ALERT: U.S. Boxed Warning

Addiction, abuse, and misuse:

Pentazocine exposes patients and other users to the risks of opioid addiction, abuse, and misuse, which can lead to overdose and death. Assess each patient’s risk prior to prescribing pentazocine, and monitor all patients regularly for the development of these behaviors and conditions.

Life-threatening respiratory depression:

Serious, life-threatening, or fatal respiratory depression may occur with use of pentazocine. Monitor for respiratory depression, especially during initiation of pentazocine or following a dose increase.

Neonatal opioid withdrawal syndrome:

Prolonged use of pentazocine during pregnancy can result in neonatal opioid withdrawal syndrome, which may be life-threatening if not recognized and treated, and requires management according to protocols developed by neonatology experts. If opioid use is required for a prolonged period in a pregnant woman, advise the patient of the risk of neonatal opioid withdrawal syndrome and ensure that appropriate treatment will be available.

Risks from concomitant use with benzodiazepines or other CNS depressants:

Concomitant use of opioids with benzodiazepines or other CNS depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. Reserve concomitant prescribing of pentazocine and benzodiazepines or other CNS depressants for use in patients for whom alternative treatment options are inadequate. Limit dosages and durations to the minimum required. Follow patients for signs and symptoms of respiratory depression and sedation.

Warnings/Precautions

Concerns related to adverse effects:

• Cardiovascular effects: May increase systemic and pulmonary arterial pressure and systemic vascular resistance; use with caution in patients who may not tolerate these alterations in hemodynamics (eg, acute myocardial infarction [MI]).

• CNS depression: May cause CNS depression, which may impair physical or mental abilities; patients must be cautioned about performing tasks which require mental alertness (eg, operating machinery or driving).

• Hypotension: May cause severe hypotension (including orthostatic hypotension and syncope); use with caution in patients with hypovolemia, cardiovascular disease (including acute MI), or drugs which may exaggerate hypotensive effects (including phenothiazines or general anesthetics). Monitor for symptoms of hypotension following initiation or dose titration. Avoid use in patients with circulatory shock.

• Injection-site reactions: Severe sclerosis of the skin, subcutaneous tissues, and underlying muscle has occurred at the injection-site following multiple injections; avoid SubQ use unless absolutely necessary; rotate sites of injection.

• Respiratory depression: [US Boxed Warning]: Serious, life-threatening, or fatal respiratory depression may occur. Monitor closely for respiratory depression, especially during initiation or dose escalation. Carbon dioxide retention from opioid-induced respiratory depression can exacerbate the sedating effects of opioids. Patients and caregivers should be educated on how to recognize respiratory depression and the importance of getting emergency assistance immediately (eg, calling 911) in the event of known or suspected overdose.

Disease-related concerns:

• Abdominal conditions: May obscure diagnosis or clinical course of patients with acute abdominal conditions.

• Adrenocortical insufficiency: Use with caution in patients with adrenal insufficiency, including Addison disease. Long-term opioid use may cause secondary hypogonadism, which may lead to mood disorders and osteoporosis (Brennan 2013).

• Biliary tract impairment: Use with caution in patients with biliary tract dysfunction or acute pancreatitis; opioids may cause constriction of sphincter of Oddi.

• CNS depression/coma: Avoid use in patients with impaired consciousness or coma as these patients are susceptible to intracranial effects of CO2 retention.

• Delirium tremens: Use with caution in patients with delirium tremens.

• Head trauma: Use with extreme caution in patients with head injury, intracranial lesions, or elevated intracranial pressure (ICP); exaggerated elevation of ICP may occur.

• Hepatic impairment: Use with caution in patients with hepatic impairment.

• Obesity: Use with caution in patients who are morbidly obese.

• Prostatic hyperplasia/urinary stricture: Use with caution in patients with prostatic hyperplasia and/or urinary stricture.

• Psychosis: Use with caution in patients with toxic psychosis.

• Renal impairment: Use with caution in patients with renal impairment.

• Respiratory disease: Use with caution and monitor for respiratory depression in patients with significant chronic obstructive pulmonary disease or cor pulmonale, and those with a substantially decreased respiratory reserve, hypoxia, hypercapnia, or preexisting respiratory depression, particularly when initiating and titrating therapy; critical respiratory depression may occur, even at therapeutic dosages. Consider the use of alternative nonopioid analgesics in these patients.

• Seizures: Use with caution in patients with a history of seizure disorders; may cause or exacerbate preexisting seizures.

• Sleep-related disorders: Opioid use increases the risk for sleep-related disorders (eg, central sleep apnea, hypoxemia) in a dose-dependent fashion; use with caution.

• Thyroid dysfunction: Use with caution in patients with thyroid dysfunction.

Concurrent drug therapy issues:

• Alcohol: Patients should not consume alcoholic beverages or use prescription or nonprescription products containing alcohol while taking pentazocine.

• Benzodiazepines or other CNS depressants: [US Boxed Warning]: Concomitant use of opioids with benzodiazepines or other CNS depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. Reserve concomitant prescribing of pentazocine and benzodiazepines or other CNS depressants for use in patients for whom alternative treatment options are inadequate. Limit dosage and durations to the minimum required and follow patients for signs and symptoms of respiratory depression and sedation. Consider prescribing naloxone for emergency treatment of opioid overdose in patients taking benzodiazepines or other CNS depressants concomitantly with opioids.

Special populations:

• Cachectic or debilitated patients: Use with caution in cachectic or debilitated patients; there is a greater potential for critical respiratory depression, even at therapeutic dosages. Consider the use of alternative nonopioid analgesics in these patients.

• Elderly: Use with caution in elderly patients; may be more sensitive to adverse effects. Consider the use of alternative nonopioid analgesics in these patients.

• Neonates: Neonatal withdrawal syndrome: [US Boxed Warning]: Prolonged use of opioids during pregnancy can cause neonatal withdrawal syndrome, which may be life-threatening if not recognized and treated according to protocols developed by neonatology experts. If opioid use is required for a prolonged period in a pregnant woman, advise the patient of the risk of neonatal opioid withdrawal syndrome and ensure that appropriate treatment will be available. Signs and symptoms include irritability, hyperactivity and abnormal sleep pattern, high pitched cry, tremor, vomiting, diarrhea and failure to gain weight. Onset, duration and severity depend on the drug used, duration of use, maternal dose, and rate of drug elimination by the newborn.

Dosage form specific issues:

• Sulfites: Some preparations may contain sulfites which may cause allergic reactions.

Other warnings/precautions:

• Abuse/misuse/diversion: [US Boxed Warning]: Pentazocine exposes patients and other users to the risks of addiction, abuse, and misuse, potentially leading to overdose and death. Assess each patient's risk prior to prescribing; monitor all patients regularly for development of these behaviors or conditions. Use with caution in patients with a history of drug abuse or acute alcoholism; potential for drug dependency exists.

• Accidental ingestion: Oral tablet [Canadian product]: Accidental ingestion of even one dose of pentazocine, especially in children, can result in a fatal overdose.

• Appropriate use: Oral tablet [Canadian product]: Tablets are intended for oral administration only; do not administer rectally.

• Naloxone access: Discuss the availability of naloxone with all patients who are prescribed opioid analgesics, as well as their caregivers, and consider prescribing it to patients who are at increased risk of opioid overdose. These include patients who are also taking benzodiazepines or other CNS depressants, have an opioid use disorder (OUD) (current or history of), or have experienced a previous opioid overdose. Additionally, health care providers should consider prescribing naloxone to patients prescribed medications to treat OUD; patients at risk of opioid overdose even if they are not taking an opioid analgesic or medication to treat OUD; and patients taking opioids, including methadone or buprenorphine for OUD, if they have household members, including children, or other close contacts at risk for accidental ingestion or opioid overdose. Inform patients and caregivers on options for obtaining naloxone (eg, by prescription, directly from a pharmacist, a community-based program) as permitted by state dispensing and prescribing guidelines. Educate patients and caregivers on how to recognize respiratory depression, proper administration of naloxone, and getting emergency help (FDA 2020).

• Optimal regimen: An opioid-containing analgesic regimen should be tailored to each patient's needs and based upon the type of pain being treated (acute versus chronic), the route of administration, degree of tolerance for opioids (naive versus chronic user), age, weight, and medical condition. The optimal analgesic dose varies widely among patients; doses should be titrated to pain relief/prevention.

• Withdrawal: Concurrent use of agonist/antagonist analgesics may precipitate withdrawal symptoms and/or reduced analgesic efficacy in patients following prolonged therapy with mu opioid agonists. Taper dose to decrease risk of withdrawal symptoms.

Monitoring Parameters

Pain relief, respiratory and mental status, blood pressure; bowel function; signs/symptoms of misuse, abuse and addiction; signs or symptoms of hypogonadism or hypoadrenalism (Brennan 2013)

Reproductive Considerations

Long-term opioid use may cause secondary hypogonadism, which may lead to sexual dysfunction or infertility in men and women (Brennan 2013).

Pregnancy Considerations

Pentazocine crosses the placenta (Beckett 1967; Moore 1973).

According to some studies, maternal use of opioids may be associated with birth defects (including neural tube defects, congenital heart defects, and gastroschisis), poor fetal growth, stillbirth, and preterm delivery (CDC [Dowell 2016]). Opioids used as part of obstetric analgesia/anesthesia during labor and delivery may temporarily affect the fetal heart rate (ACOG 209 2019).

[US Boxed Warning]: Prolonged use of pentazocine during pregnancy can result in neonatal opioid withdrawal syndrome, which may be life-threatening if not recognized and treated, and requires management according to protocols developed by neonatology experts. If opioid use is required for a prolonged period in a pregnant woman, advise the patient of the risk of neonatal opioid withdrawal syndrome and ensure that appropriate treatment will be available. If chronic opioid exposure occurs in pregnancy, adverse events in the newborn (including withdrawal) may occur; monitoring of the neonate is recommended. The minimum effective dose should be used if opioids are needed (Chou 2009). Neonatal abstinence syndrome following opioid exposure may present with autonomic (eg, fever, temperature instability), gastrointestinal (eg, diarrhea, vomiting, poor feeding/weight gain), or neurologic (eg, high-pitched crying, increased muscle tone, irritability, seizure, tremor) symptoms (Dow 2012; Hudak 2012). Neonatal abstinence syndrome has been reported following prolonged use of pentazocine during pregnancy.

Pentazocine is approved for pain relief during labor; however, other agents are more commonly used (ACOG 209 2019).

Patient Education

What is this drug used for?

• It is used to ease pain.

• It may be given to you for other reasons. Talk with the doctor.

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

• Vomiting

• Nausea

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

• Trouble breathing

• Slow breathing

• Shallow breathing

• Noisy breathing

• Serotonin syndrome like dizziness, severe headache, agitation, sensing things that seem real but are not, fast heartbeat, abnormal heartbeat, flushing, tremors, sweating a lot, change in balance, severe nausea, or severe diarrhea

• Adrenal gland problems like severe nausea, vomiting, severe dizziness, passing out, muscle weakness, severe fatigue, mood changes, lack of appetite, or weight loss

• Severe dizziness

• Passing out

• Severe fatigue

• Mood changes

• Confusion

• Seizures

• Severe constipation

• Severe abdominal pain

• Sexual dysfunction (males)

• No menstrual periods

• Decreased sex drive

• Trouble getting pregnant

• Severe injection site irritation

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.

Note: This is not a comprehensive list of all side effects. Talk to your doctor if you have questions.

Consumer Information Use and Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a limited summary of general information about the medicine's uses from the patient education leaflet and is not intended to be comprehensive. This limited summary does NOT include all information available about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not intended to provide medical advice, diagnosis or treatment and does not replace information you receive from the healthcare provider. For a more detailed summary of information about the risks and benefits of using this medicine, please speak with your healthcare provider and review the entire patient education leaflet.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.