Pentazocine (Monograph)

Brand name: Talwin
Drug class: Opioid Partial Agonists
VA class: CN101
CAS number: 64024-15-3

Pentazocine Hydrochloride, Pentazocine Lactate is also contained as an ingredient in the following combinations:
Pentazocine and Naloxone Hydrochlorides

Medically reviewed by Drugs.com on Apr 9, 2025. Written by ASHP.

Introduction

Analgesic; synthetic opiate partial agonist.^a

Uses for Pentazocine

Pain

Relief of moderate to severe pain^{a b c} such as that associated with acute and chronic medical disorders including cancer, orthopedic problems, renal or biliary colic, and dental surgery.^a

Has been used parenterally for preoperative sedation and analgesia and as an adjunct to surgical anesthesia;^{a c} however, parenteral dosage form is no longer commercially available in US.

Also has been used parenterally for obstetric analgesia during labor.^{a c}

Oral dosage form reformulated to contain small amount of naloxone hydrochloride (opiate antagonist) to potentially eliminate misuse via parenteral injection by opiate addicts and drug abusers.^{a b} Naloxone is inactive when administered orally in the amount (0.5 mg) present in the oral formulation and does not affect the efficacy of pentazocine when administered orally.^{a b}

In symptomatic treatment of acute pain, reserve opiate analgesics for pain resulting from severe injuries, severe medical conditions, or surgical procedures, or when nonopiate alternatives for relieving pain and restoring function are expected to be ineffective or are contraindicated.^{431 432 433 435} Use smallest effective dosage for shortest possible duration since long-term opiate use often begins with treatment of acute pain.^{411 431 434 435} Optimize concomitant use of other appropriate therapies.^{432 434 435} (See Managing Opiate Therapy for Acute Pain under Dosage and Administration.)

Generally use opiates for management of chronic pain (i.e., pain lasting >3 months or past the time of normal tissue healing^{410 411 412 413} ) that is not associated with active cancer treatment, palliative care, or end-of-life care only if other appropriate nonpharmacologic and nonopiate pharmacologic strategies have been ineffective and expected benefits for both pain relief and functional improvement are anticipated to outweigh risks.^{411 412 413 414 422 429}

If used for chronic pain, opiate analgesics should be part of an integrated approach that also includes appropriate nonpharmacologic modalities (e.g., cognitive-behavioral therapy, relaxation techniques, biofeedback, functional restoration, exercise therapy, certain interventional procedures) and other appropriate pharmacologic therapies (e.g., nonopiate analgesics, analgesic adjuncts such as selected anticonvulsants and antidepressants for certain neuropathic pain conditions).^{411 412 413 422 429}

Available evidence insufficient to determine whether long-term opiate therapy for chronic pain results in sustained pain relief or improvements in function and quality of life^{411 423 431 432 436} or is superior to other pharmacologic or nonpharmacologic treatments.⁴³² Use is associated with serious risks (e.g., opiate use disorder [OUD], overdose).^{411 431 436} (See Managing Opiate Therapy for Chronic Noncancer Pain under Dosage and Administration.)

Pentazocine Dosage and Administration

General

• If pentazocine hydrochloride tablets containing small amount of naloxone hydrochloride are ground up and solubilized for parenteral administration, the naloxone will antagonize the effects of pentazocine and will precipitate withdrawal symptoms in drug abusers who are dependent on opiates.^{a b}

Managing Opiate Therapy for Acute Pain

• Optimize concomitant use of other appropriate therapies.^{432 434 435}

• When opiate analgesia required, use conventional (immediate-release) opiates in smallest effective dosage and for shortest possible duration, since long-term opiate use often begins with treatment of acute pain.^{411 431 434 435}

• Consider prescribing naloxone concomitantly for patients who are at increased risk of opiate overdosage^{411 431 750} or who have household members, including children, or other close contacts who are at risk for accidental ingestion or overdosage.⁷⁵⁰ (See Respiratory Effects under Cautions.)

• When sufficient for pain management, use lower-potency opiate analgesics given in conjunction with acetaminophen or an NSAIA on as-needed (“prn”) basis.⁴³²

• For acute pain not related to trauma or surgery, limit prescribed quantity to amount needed for expected duration of pain severe enough to require opiate analgesia (generally ≤3 days and rarely >7 days).^{411 433 434 435} Do not prescribe larger quantities for use in case pain continues longer than expected;^{411 432} instead, reevaluate patient if severe acute pain does not remit.^{411 431 435}

• For moderate to severe postoperative pain, provide opiate analgesic as part of a multimodal regimen that also includes acetaminophen and/or NSAIAs and other pharmacologic (e.g., certain anticonvulsants, regional local anesthetic techniques) and nonpharmacologic therapy as appropriate.^{430 431 432}

• Oral administration of conventional opiate analgesics generally preferred over IV administration in postoperative patients who can tolerate oral therapy.^{430 431}

• Scheduled (around-the-clock) dosing frequently is required during immediate postoperative period or following major surgery.^{430 432} When repeated parenteral administration is required, IV patient-controlled analgesia (PCA) generally is recommended.^{430 431}

Managing Opiate Therapy for Chronic Noncancer Pain

• Although specific recommendations may vary, common elements in clinical guideline recommendations include risk mitigation strategies, upper dosage thresholds, careful dosage titration, and consideration of risks associated with particular opiates and formulations, coexisting diseases, and concomitant drug therapy.^{410 411 414 415 423}

• Prior to initiating therapy, thoroughly evaluate patient; assess risk factors for misuse, abuse, and addiction;^{411 412 413 415 422 429} establish treatment goals (including realistic goals for pain and function); and consider how therapy will be discontinued if benefits do not outweigh risks.^{411 415}

• Regard initial opiate therapy for chronic noncancer pain as a therapeutic trial that will be continued only if there are clinically meaningful improvements in pain and function that outweigh treatment risks.^{411 412 413}

• Prior to and periodically during therapy, discuss with patients known risks and realistic benefits and patient and clinician responsibilities for managing therapy.^{411 412 413 414 415}

• Some experts recommend initiating opiate therapy for chronic noncancer pain with conventional (immediate-release) opiate analgesics prescribed at lowest effective dosage.^{411 415} Individualize opiate selection, initial dosage, and dosage titration based on patient’s health status, prior opiate use, attainment of therapeutic goals, and predicted or observed harms.^{412 413}

• Evaluate benefits and harms within 1–4 weeks following initiation of therapy or dosage increase^{411 413} and reevaluate on ongoing basis (e.g., at least every 3 months⁴¹¹ ) throughout therapy.^{411 412 413} Document pain intensity and level of functioning and assess progress toward therapeutic goals, presence of adverse effects, and adherence to prescribed therapies.^{412 413 422 423} Anticipate and manage common adverse effects (e.g., constipation, nausea and vomiting, cognitive and psychomotor impairment).^{412 413 415} If benefits do not outweigh harms, optimize other therapies and taper opiate to lower dosage or taper and discontinue opiate.^{411 412 413 415}

• When repeated dosage increases required, evaluate potential causes and reassess relative benefits and risks.^{412 413} Although evidence is limited, some experts state that opiate rotation may be considered in patients with intolerable adverse effects or inadequate benefit despite dosage increases.^{412 413 415}

• Higher dosages require particular caution,^{410 412 415} including more frequent and intensive monitoring or referral to specialist.^{411 412 413} Greater benefits of high-dose opiates for chronic pain not established in controlled clinical studies; higher dosages associated with increased risks (motor vehicle accidents, overdosage, OUD).^{411 415 423 424 425 426}

• CDC states that primary care clinicians should carefully reassess individual benefits and risks before prescribing dosages equivalent to ≥50 mg of morphine sulfate daily for chronic pain and should avoid dosages equivalent to ≥90 mg of morphine sulfate daily or carefully justify decision to prescribe such dosages.⁴¹¹ Other experts recommend consulting a pain management specialist before exceeding a dosage equivalent to 80–120 mg of morphine sulfate daily.^{423 431} Some states have established opiate dosage thresholds (e.g., maximum daily dosages that can be prescribed, dosage thresholds at which consultation with specialist is mandated or recommended)^{411 420 421 423} or have mandated risk-management strategies (e.g., review of state prescription drug monitoring program [PDMP] data prior to prescribing).^{411 419 423}

• Recommended strategies for managing risks include written treatment agreements or plans (e.g., “contracts”), urine drug testing, review of state PDMP data, and risk assessment and monitoring tools.^{410 411 412 413 414 415 422 423 429}

• Taper and discontinue opiate therapy if patient engages in serious or repeated aberrant drug-related behaviors or drug abuse or diversion.^{412 413 415} Offer or arrange treatment for patients with OUD.^{411 412 413}

• Consider prescribing naloxone concomitantly for patients who are at increased risk of opiate overdosage^{411 431 750} or who have household members, including children, or other close contacts who are at risk for accidental ingestion or overdosage.⁷⁵⁰ (See Respiratory Effects under Cautions.)

Administration

Administer orally.^b Pentazocine lactate has been administered by IV, IM, or sub-Q injection;^c however, injection no longer commercially available in US.

Dosage

Available as pentazocine and naloxone hydrochlorides (tablets); dosage expressed in terms of the bases.^{100 101}

Use lowest effective dosage and shortest duration of therapy consistent with treatment goals of the patient.^{411 413 431 432 435}

Adjust dosage according to severity of pain, physical status of the patient, and other drugs that the patient is receiving.^a

When used concomitantly with other CNS depressants, use lowest effective dosages and shortest possible duration of concomitant therapy.^{700 703} (See Specific Drugs and Laboratory Tests under Interactions.)

Adults

Pain

Oral

Initially, 50 mg every 3–4 hours.^{a b} Increase dosage to 100 mg when needed (maximum 600 mg daily).^{a b}

Prescribing Limits

Adults

Pain

For acute pain not related to trauma or surgery, limit prescribed quantity to amount needed for the expected duration of pain severe enough to require opiate analgesia (generally ≤3 days and rarely >7 days).^{411 433 434 435}

CDC recommends that primary care clinicians carefully reassess individual benefits and risks before prescribing dosages equivalent to ≥50 mg of morphine sulfate daily for chronic pain and avoid dosages equivalent to ≥90 mg of morphine sulfate daily or carefully justify their decision to prescribe such dosages.⁴¹¹ Other experts recommend consulting a pain management specialist before exceeding a dosage equivalent to 80–120 mg of morphine sulfate daily.^{423 431}

Some states have set prescribing limits for opiate analgesics (e.g., maximum daily dosages that can be prescribed, dosage thresholds at which consultation with a specialist is mandated or recommended).^{411 420 421 423}

Oral

Maximum 600 mg daily.^b

Special Populations

Hepatic Impairment

Doses and/or frequency of administration may need to be decreased, particularly when administered orally, in patients with hepatic impairment (e.g., cirrhosis).^{144 145 155}

Geriatric Patients

Cautious dosage selection recommended; initiate therapy at the lower end of the usual range.^{b c}

Cautions for Pentazocine

Contraindications

• Known hypersensitivity to pentazocine or any ingredient in the formulation.^{b c d}

Warnings/Precautions

Warnings

Abuse Potential

Possible tolerance, psychologic dependence, and physical dependence.^{100 109 124 125 126 127 128 129 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 186}

Prescribe cautiously for patients who are emotionally unstable or have a history of opiate abuse; closely supervise these patients when therapy for more than 4 or 5 days is contemplated.^a Avoid unnecessary increases in dosage or frequency of administration; avoid use in anticipation of pain.^a

If tablets are ground up and solubilized for parenteral administration, the naloxone will antagonize the effects of pentazocine and can precipitate withdrawal in individuals physically dependent on opiates.^{100 106 161} However, since naloxone is inactive when administered orally in the amount present in the tablets, the tablets are still subject to misuse and abuse by the oral route.¹⁰⁰

Pentazocine has been abused in combination with tripelennamine (no longer commercially available in US) (T’s and blues) via parenteral injection by opiate addicts and drug abusers in an attempt to provide effects similar to those of IV heroin.^{106 109 110 111 112 113 114 115 116 117 118 119 130 186}

Respiratory Effects

Possible respiratory depression (decreased rate and depth of respiration), dyspnea, and laryngospasm.^{a b}

Use with caution and in low doses in patients with impaired respiration caused by other drugs, uremia, or severe infection and in patients with severely limited respiratory reserve, bronchial asthma or other obstructive respiratory conditions, or cyanosis.^{b c}

Pentazocine-induced respiratory depression can be reversed by naloxone.^b

Routinely discuss availability of the opiate antagonist naloxone with all patients receiving new or reauthorized prescriptions for opiate analgesics, including pentazocine.⁷⁵⁰

Consider prescribing naloxone for patients receiving opiate analgesics who are at increased risk of opiate overdosage (e.g., those receiving concomitant therapy with benzodiazepines or other CNS depressants, those with history of opiate or substance use disorder, those with medical conditions that could increase sensitivity to opiate effects, those who have experienced a prior opiate overdose)^{411 431 750} or who have household members, including children, or other close contacts who are at risk for accidental ingestion or overdosage.⁷⁵⁰ Even if patients are not receiving an opiate analgesic, consider prescribing naloxone if the patient is at increased risk of opiate overdosage (e.g., those with current or past diagnosis of OUD, those who have experienced a prior opiate overdose).⁷⁵⁰

Concomitant Use with Benzodiazepines or Other CNS Depressants

Concomitant use of opiate agonists or opiate partial agonists, including pentazocine, and benzodiazepines or other CNS depressants (e.g., anxiolytics, sedatives, hypnotics, tranquilizers, muscle relaxants, general anesthetics, antipsychotics, other opiates, alcohol) may result in profound sedation, respiratory depression, coma, and death.^{416 417 418 700 701 702 703} Substantial proportion of fatal opiate overdoses involve concurrent benzodiazepine use.^{416 417 418 435 700 701}

Reserve concomitant use of pentazocine and other CNS depressants for patients in whom alternative treatment options are inadequate.^{700 703} (See Specific Drugs and Laboratory Tests under Interactions.)

Local Effects

Possible ulceration and severe sclerosis of the skin, subcutaneous tissues, and underlying muscle following repeated injection.^c

Patients Dependent on Opiates

Partial opiate antagonist.^{b c} Use with caution in patients who have been chronically receiving opiates (including methadone); pentazocine does not suppress the abstinence syndrome in these patients; high doses may precipitate withdrawal symptoms.^{b c}

CNS Depression

Performance of activities requiring mental alertness and physical coordination may be impaired.^{b c}

Concurrent use of other CNS depressants may potentiate CNS depression^{b c} and may result in profound sedation, respiratory depression, coma, or death.^{700 703} (See Concomitant Use with Benzodiazepines or Other CNS Depressants under Cautions.)

Adrenal Insufficiency

Adrenal insufficiency reported in patients receiving opiate agonists or opiate partial agonists.⁴⁰⁰ Manifestations are nonspecific and may include nausea, vomiting, anorexia, fatigue, weakness, dizziness, and hypotension.⁴⁰⁰

If adrenal insufficiency is suspected, perform appropriate laboratory testing promptly and provide physiologic (replacement) dosages of corticosteroids; taper and discontinue the opiate agonist or partial agonist to allow recovery of adrenal function.⁴⁰⁰ If the opiate agonist or partial agonist can be discontinued, perform follow-up assessment of adrenal function to determine if corticosteroid replacement therapy can be discontinued.⁴⁰⁰ In some patients, switching to a different opiate improved symptoms.⁴⁰⁰

Withdrawal Effects

Abrupt discontinuance after prolonged use may result in withdrawal symptoms (e.g., abdominal cramps, vomiting, increased temperature, sweating, chills, restlessness, anxiety, lethargy, rhinorrhea, sneezing, lacrimation).^{166 169 172 173 174 175 176 181 182 184 185}

Opiates occasionally have been used in the management of pentazocine withdrawal;^{169 172 174 182 183} benzodiazepines also have been used in a limited number of individuals.¹⁸¹

Head Injury and Increased Intracranial Pressure

Potential for elevation of CSF pressure as a result of vasodilation following carbon dioxide retention.^{a c} Opiate effects may obscure the existence, extent, or course of intracranial pathology.^{b c} Use in patients with head injury, other intracranial lesions, or preexisting elevation in intracranial pressure only if the potential benefits justify the possible risks.^{a b c}

Acute CNS Manifestations

Hallucinations (usually visual), disorientation, and confusion have occurred following therapeutic doses but usually have cleared spontaneously within several hours.^{b c}

If such symptoms occur, closely observe the patient and check vital signs.^{b c} Caution if pentazocine is reinstated, since acute CNS reactions may recur.^{b c}

Acute MI

Possible increased systemic and pulmonary arterial pressure and systemic vascular resistance with IV administration in patients with acute MI.^c

Administer oral pentazocine with caution in patients with acute MI accompanied by nausea and vomiting.^b

General Precautions

Biliary Tract Surgery

Possible spasm of Oddi’s sphincter; use with caution in patients about to undergo biliary tract surgery.^{b c}

Seizures

Possible occurrence of seizures following administration in seizure-prone patients.^{b c} Use with caution in such patients.^{b c}

Hypogonadism

Hypogonadism or androgen deficiency reported in patients receiving long-term opiate agonist or opiate partial agonist therapy;^{400 401 402 403 404} causality not established.⁴⁰⁰ Manifestations may include decreased libido, impotence, erectile dysfunction, amenorrhea, or infertility.⁴⁰⁰ Perform appropriate laboratory testing in patients with manifestations of hypogonadism.⁴⁰⁰

Specific Populations

Pregnancy

Category C.^b

Safe use in pregnant women (except during labor) not established.^{b c} Should not be administered to women who are pregnant unless potential benefits outweigh possible risks to fetus.^{b c} Possible abstinence (withdrawal) syndrome in neonates after prolonged maternal use during pregnancy.^{100 150 151 152 153 154}

Respiratory depression and transient apnea may occur in neonates when administered during labor and delivery;^a use with caution in women delivering premature infants.^{b c}

Lactation

Not known whether pentazocine is distributed into milk; use with caution in nursing women.^b

Pediatric Use

Safety and efficacy of oral pentazocine not established in children <12 years of age.^{a b}

Geriatric Use

Possible increased sensitivity to pentazocine in some geriatric individuals.^c

Insufficient experience with pentazocine tablets in patients ≥65 years of age to determine whether geriatric patients respond differently than younger adults.^b

Use with caution due to the greater frequency of decreased hepatic, renal, and/or cardiac function and of concomitant disease and drug therapy observed in the elderly.^{b c} May be useful to monitor renal function.^c

Select dosage with caution.^{b c} (See Geriatric Patients under Dosage and Administration.)

Hepatic Impairment

Use with caution.^{b c} Extensive liver disease may predispose to greater incidence or severity of adverse effects than would be expected from usual doses, probably as a result of decreased hepatic metabolism of the drug.^{b c}

Renal Impairment

Use with caution.^{b c}

Common Adverse Effects

Dizziness, lightheadedness, euphoria, sedation, nausea.^a

Drug Interactions

Drugs Associated with Serotonin Syndrome

Risk of serotonin syndrome when used with other serotonergic drugs.⁴⁰⁰ May occur at usual dosages.⁴⁰⁰ Symptom onset generally occurs within several hours to a few days of concomitant use, but may occur later, particularly after dosage increases.⁴⁰⁰ (See Advice to Patients.)

If concomitant use of other serotonergic drugs is warranted, monitor patients for serotonin syndrome, particularly during initiation of therapy and dosage increases.⁴⁰⁰

If serotonin syndrome is suspected, discontinue pentazocine, other opiate therapy, and/or any concurrently administered serotonergic agents.⁴⁰⁰

Specific Drugs and Laboratory Tests

Pentazocine Pharmacokinetics

Absorption

Bioavailability

Well absorbed from the GI tract^b and from IM and sub-Q injection sites.^a

Undergoes first-pass metabolism following oral administration, with <20% of an oral dose reaching systemic circulation as unchanged drug.^a

Onset

Following oral administration, onset of analgesia occurs within 15–30 minutes; peak analgesia occurs within 1–3 hours.^{a b}

Following IM or sub-Q injection, onset of analgesia occurs within 15–20 minutes; peak analgesia occurs within about 1 hour.^{a c}

Following IV administration, onset of analgesia occurs within 2–3 minutes; peak analgesia occurs within 15 minutes.^{a c}

Duration

Following oral administration, duration of analgesia is ≥3 hours.^b

Following IM or sub-Q injection, duration of analgesia is about 2 hours; following IV administration, duration is about 1 hour.^a

Special Populations

In patients with hepatic dysfunction, oral bioavailability may be substantially increased; about 60–70% of an oral dose is reportedly absorbed unchanged in individuals with cirrhosis.^{144 145}

Distribution

Extent

Widely distributed in the body.^a

Crosses the placenta; neonatal serum concentrations reported to average about 65% of maternal concentrations at delivery.^{a b}

Not known whether pentazocine is distributed into milk.^b

Plasma Protein Binding

About 60%.^a

Elimination

Metabolism

Metabolized in the liver.^b

Elimination Route

Excreted principally in urine.^b Less unchanged drug appears to be excreted in urine after oral administration than after IV administration.^a

Half-life

2–3 hours.^b

Special Populations

In patients with hepatic impairment, clearance may be decreased and elimination half-life prolonged.^{144 145 155}

In geriatric patients, elimination half-life may be prolonged and systemic exposure to pentazocine increased.^c

Stability

Storage

Oral

Tablets

25°C (may be exposed to 15–30°C).^b

Actions

• Believed to be a competitive antagonist at μ opiate receptors and an agonist at κ and Σ opiate receptors.^a

• Analgesic and respiratory depressant activity apparently results mainly from the l-isomer.^a

• Produces respiratory depression, sedation, miosis, and antitussive effects.^a

• In low doses (15 mg IM), pentazocine inhibits GI motility and slows the rate of gastric emptying; higher doses (30–45 mg) reportedly increase intestinal transit time and produce less elevation of biliary pressure than equianalgesic doses of morphine.^a

Advice to Patients

• Potential for pentazocine to impair mental alertness or physical coordination; do not drive or operate machinery until effects on individual are known.^b

• Risk of respiratory depression following overdosage.⁷⁵⁰ Advise patients of the benefits of naloxone following opiate overdose and of their options for obtaining the drug.⁷⁵⁰

• Risk of potentially fatal additive effects (e.g., profound sedation, respiratory depression, coma) if used concomitantly with benzodiazepines or other CNS depressants, including alcohol and other opiates, either therapeutically or illicitly; avoid concomitant use unless such use is supervised by clinician.^{700 703} Importance of informing patients that pentazocine should not be combined with alcohol.^{700 b}

• Importance of taking exactly as prescribed; do not exceed the recommended dosage.^b

• Potential risk of serotonin syndrome with concurrent use of pentazocine and other serotonergic agents.⁴⁰⁰ Importance of immediately contacting clinician if manifestations of serotonin syndrome (e.g., agitation, hallucinations, tachycardia, labile BP, fever, excessive sweating, shivering, shaking, muscle stiffness, twitching, loss of coordination, nausea, vomiting, diarrhea) develop.⁴⁰⁰

• Potential risk of adrenal insufficiency.⁴⁰⁰ Importance of contacting clinician if manifestations of adrenal insufficiency (e.g., nausea, vomiting, loss of appetite, fatigue, weakness, dizziness, hypotension) develop.⁴⁰⁰

• Possible risk (although causality not established) of hypogonadism or androgen deficiency with long-term opiate agonist or partial agonist use.⁴⁰⁰ Importance of informing clinician if decreased libido, impotence, erectile dysfunction, amenorrhea, or infertility occurs.⁴⁰⁰

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs and alcohol consumption.^b

• Importance of women informing their clinician if they are or plan to become pregnant or plan to breast-feed.^b

• Importance of advising patients of other important precautionary information.^{b c} (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

Subject to control under the Federal Controlled Substances Act of 1970 as schedule IV (C-IV) drug. May be subject to more stringent control in some states.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

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