Skip to main content

Pentazocine

Class: Opiate Partial Agonists
VA Class: CN101
CAS Number: 64024-15-3
Brands: Talwin

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

Medically reviewed by Drugs.com on Mar 29, 2021. Written by ASHP.

Warning

    Concomitant Use with Benzodiazepines or Other CNS Depressants
  • Concomitant use of opiates with benzodiazepines or other CNS depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death.

  • Reserve concomitant use of opiate analgesics and benzodiazepines or other CNS depressants for patients in whom alternative treatment options are inadequate; use lowest effective dosages and shortest possible duration of concomitant therapy and monitor closely for respiratory depression and sedation. (See Specific Drugs and Laboratory Tests under Interactions.)

Risk Evaluation and Mitigation Strategy (REMS):

FDA approved a REMS for pentazocine to ensure that the benefits outweigh the risk. The REMS may apply to one or more preparations of pentazocine and consists of the following: medication guide and elements to assure safe use. See https://www.accessdata.fda.gov/scripts/cder/rems/.

Introduction

Analgesic; synthetic opiate partial agonist.

Uses for Pentazocine

Pain

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

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

Also has been used parenterally for obstetric analgesia during labor.

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. 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.

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. Use smallest effective dosage for shortest possible duration since long-term opiate use often begins with treatment of acute pain. Optimize concomitant use of other appropriate therapies. (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 ) 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.

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).

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 or is superior to other pharmacologic or nonpharmacologic treatments. Use is associated with serious risks (e.g., opiate use disorder [OUD], overdose). (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.

Managing Opiate Therapy for Acute Pain

  • Optimize concomitant use of other appropriate therapies.

  • 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.

  • Consider prescribing naloxone concomitantly for patients who are at increased risk of opiate overdosage or who have household members, including children, or other close contacts who are at risk for accidental ingestion or overdosage. (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.

  • 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). Do not prescribe larger quantities for use in case pain continues longer than expected; instead, reevaluate patient if severe acute pain does not remit.

  • 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.

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

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

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.

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

  • 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.

  • Prior to and periodically during therapy, discuss with patients known risks and realistic benefits and patient and clinician responsibilities for managing therapy.

  • Some experts recommend initiating opiate therapy for chronic noncancer pain with conventional (immediate-release) opiate analgesics prescribed at lowest effective dosage. 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.

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

  • When repeated dosage increases required, evaluate potential causes and reassess relative benefits and risks. 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.

  • Higher dosages require particular caution, including more frequent and intensive monitoring or referral to specialist. 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).

  • 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. Other experts recommend consulting a pain management specialist before exceeding a dosage equivalent to 80–120 mg of morphine sulfate daily. 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) or have mandated risk-management strategies (e.g., review of state prescription drug monitoring program [PDMP] data prior to prescribing).

  • 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.

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

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

Administration

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

Dosage

Available as pentazocine and naloxone hydrochlorides (tablets); dosage expressed in terms of the bases.

Use lowest effective dosage and shortest duration of therapy consistent with treatment goals of the patient.

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

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

Adults

Pain
Oral

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

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).

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. Other experts recommend consulting a pain management specialist before exceeding a dosage equivalent to 80–120 mg of morphine sulfate daily.

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).

Oral

Maximum 600 mg daily.

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).

Geriatric Patients

Cautious dosage selection recommended; initiate therapy at the lower end of the usual range.

Cautions for Pentazocine

Contraindications

  • Known hypersensitivity to pentazocine or any ingredient in the formulation.

Warnings/Precautions

Warnings

Abuse Potential

Possible tolerance, psychologic dependence, and physical dependence.

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. Avoid unnecessary increases in dosage or frequency of administration; avoid use in anticipation of pain.

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. 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.

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.

Respiratory Effects

Possible respiratory depression (decreased rate and depth of respiration), dyspnea, and laryngospasm.

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.

Pentazocine-induced respiratory depression can be reversed by naloxone.

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

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) or who have household members, including children, or other close contacts who are at risk for accidental ingestion or overdosage. 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).

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. Substantial proportion of fatal opiate overdoses involve concurrent benzodiazepine use.

Reserve concomitant use of pentazocine and other CNS depressants for patients in whom alternative treatment options are inadequate. (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.

Patients Dependent on Opiates

Partial opiate antagonist. 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.

CNS Depression

Performance of activities requiring mental alertness and physical coordination may be impaired.

Concurrent use of other CNS depressants may potentiate CNS depression and may result in profound sedation, respiratory depression, coma, or death. (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. Manifestations are nonspecific and may include nausea, vomiting, anorexia, fatigue, weakness, dizziness, and hypotension.

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. 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. In some patients, switching to a different opiate improved symptoms.

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).

Opiates occasionally have been used in the management of pentazocine withdrawal; benzodiazepines also have been used in a limited number of individuals.

Head Injury and Increased Intracranial Pressure

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

Acute CNS Manifestations

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

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

Acute MI

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

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

General Precautions

Biliary Tract Surgery

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

Seizures

Possible occurrence of seizures following administration in seizure-prone patients. Use with caution in such patients.

Hypogonadism

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

Specific Populations

Pregnancy

Category C.

Safe use in pregnant women (except during labor) not established. Should not be administered to women who are pregnant unless potential benefits outweigh possible risks to fetus. Possible abstinence (withdrawal) syndrome in neonates after prolonged maternal use during pregnancy.

Respiratory depression and transient apnea may occur in neonates when administered during labor and delivery; use with caution in women delivering premature infants.

Lactation

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

Pediatric Use

Safety and efficacy of oral pentazocine not established in children <12 years of age.

Geriatric Use

Possible increased sensitivity to pentazocine in some geriatric individuals.

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

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. May be useful to monitor renal function.

Select dosage with caution. (See Geriatric Patients under Dosage and Administration.)

Hepatic Impairment

Use with caution. 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.

Renal Impairment

Use with caution.

Common Adverse Effects

Dizziness, lightheadedness, euphoria, sedation, nausea.

Interactions for Pentazocine

Drugs Associated with Serotonin Syndrome

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

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

Specific Drugs and Laboratory Tests

Drug or Test

Interaction

Comments

Antidepressants, SSRIs (e.g., citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline), SNRIs (e.g., desvenlafaxine, duloxetine, milnacipran, venlafaxine), tricyclic antidepressants (TCAs), mirtazapine, nefazodone, trazodone, vilazodone

Risk of serotonin syndrome

If concomitant use warranted, monitor for serotonin syndrome, particularly during initiation of therapy and dosage increases

If serotonin syndrome suspected, discontinue pentazocine, the antidepressant, and/or any concurrently administered opiates or serotonergic agents

Antiemetics, 5-HT3 receptor antagonists (e.g., dolasetron, granisetron, ondansetron, palonosetron)

Risk of serotonin syndrome

If concomitant use warranted, monitor for serotonin syndrome, particularly during initiation of therapy and dosage increases

If serotonin syndrome suspected, discontinue pentazocine, the 5-HT3 receptor antagonist, and/or any concurrently administered opiates or serotonergic agents

Antipsychotics (e.g., aripiprazole, asenapine, cariprazine, chlorpromazine, clozapine, fluphenazine, haloperidol, iloperidone, loxapine, lurasidone, molindone, olanzapine, paliperidone, perphenazine, pimavanserin, quetiapine, risperidone, thioridazine, thiothixene, trifluoperazine, ziprasidone)

Risk of profound sedation, respiratory depression, coma, or death

Use concomitantly only if alternative treatment options are inadequate; use lowest effective dosages and shortest possible duration of concomitant therapy

In patients receiving pentazocine, initiate antipsychotic, if required, at lower dosage than indicated in the absence of opiate therapy and titrate based on clinical response

In patients receiving an antipsychotic, initiate pentazocine, if required, at reduced dosage and titrate based on clinical response

Monitor closely for respiratory depression and sedation

Benzodiazepines (e.g., alprazolam, chlordiazepoxide, clobazam, clonazepam, clorazepate, diazepam, estazolam, flurazepam, lorazepam, midazolam, oxazepam, quazepam, temazepam, triazolam)

Risk of profound sedation, respiratory depression, coma, or death

Whenever possible, avoid concomitant use

Use concomitantly only if alternative treatment options are inadequate; use lowest effective dosages and shortest possible duration of concomitant therapy

In patients receiving pentazocine, initiate benzodiazepine, if required for any indication other than epilepsy, at lower dosage than indicated in the absence of opiate therapy and titrate based on clinical response

In patients receiving a benzodiazepine, initiate pentazocine, if required, at reduced dosage and titrate based on clinical response

Monitor closely for respiratory depression and sedation

Consider prescribing naloxone for patients receiving opiates and benzodiazepines concomitantly

Buspirone

Risk of serotonin syndrome

If concomitant use warranted, monitor for serotonin syndrome, particularly during initiation of therapy and dosage increases

If serotonin syndrome suspected, discontinue pentazocine, buspirone, and/or any concurrently administered opiates or serotonergic agents

CNS depressants (e.g., other opiates, general anesthetics, phenothiazines or other tranquilizers, anxiolytics, alcohol)

Possible additive effects; increased risk of profound sedation, respiratory depression, hypotension, coma, or death

Use concomitantly only if alternative treatment options are inadequate; use lowest effective dosages and shortest possible duration of concomitant therapy

In patients receiving pentazocine, initiate CNS depressant, if required for any indication other than epilepsy, at lower dosage than indicated in the absence of opiate therapy and titrate based on clinical response

In patients receiving a CNS depressant, initiate pentazocine, if required, at reduced dosage and titrate based on clinical response

Monitor closely for respiratory depression and sedation

Consider prescribing naloxone for patients receiving opiates and other CNS depressants concomitantly

Avoid alcohol use

Dextromethorphan

Risk of serotonin syndrome

If concomitant use warranted, monitor for serotonin syndrome, particularly during initiation of therapy and dosage increases

If serotonin syndrome suspected, discontinue pentazocine, dextromethorphan, and/or any concurrently administered opiates or serotonergic agents

5-HT1 receptor agonists (triptans; e.g., almotriptan, frovatriptan, naratriptan, rizatriptan, sumatriptan, zolmitriptan)

Risk of serotonin syndrome

If concomitant use warranted, monitor for serotonin syndrome, particularly during initiation of therapy and dosage increases

If serotonin syndrome suspected, discontinue pentazocine, the triptan, and/or any concurrently administered opiates or serotonergic agents

Lithium

Risk of serotonin syndrome

If concomitant use warranted, monitor for serotonin syndrome, particularly during initiation of therapy and dosage increases

If serotonin syndrome suspected, discontinue pentazocine, lithium, and/or any concurrently administered opiates or serotonergic agents

MAO inhibitors (e.g., isocarboxazid, linezolid, methylene blue, phenelzine, selegiline, tranylcypromine)

Risk of serotonin syndrome

If concomitant use warranted, monitor for serotonin syndrome, particularly during initiation of therapy and dosage increases

If serotonin syndrome suspected, discontinue pentazocine, the MAO inhibitor, and/or any concurrently administered opiates or serotonergic agents

Sedative/hypnotic agents (e.g., butabarbital, eszopiclone, pentobarbital, ramelteon, secobarbital, suvorexant, zaleplon, zolpidem)

Risk of profound sedation, respiratory depression, coma, or death

Use concomitantly only if alternative treatment options are inadequate; use lowest effective dosages and shortest possible duration of concomitant therapy

In patients receiving pentazocine, initiate sedative/hypnotic, if required, at lower dosage than indicated in the absence of opiate therapy and titrate based on clinical response

In patients receiving a sedative/hypnotic, initiate pentazocine, if required, at reduced dosage and titrate based on clinical response

Monitor closely for respiratory depression and sedation

Skeletal muscle relaxants (e.g., baclofen, carisoprodol, chlorzoxazone, cyclobenzaprine, dantrolene, metaxalone, methocarbamol, orphenadrine, tizanidine)

Risk of profound sedation, respiratory depression, coma, or death

Cyclobenzaprine: Increased risk of adverse effects (e.g., seizures, serotonin syndrome)

Use concomitantly only if alternative treatment options are inadequate; use lowest effective dosages and shortest possible duration of concomitant therapy

In patients receiving pentazocine, initiate skeletal muscle relaxant, if required, at lower dosage than indicated in the absence of opiate therapy and titrate based on clinical response

In patients receiving a skeletal muscle relaxant, initiate pentazocine, if required, at reduced dosage and titrate based on clinical response

Monitor closely for respiratory depression and sedation

Cyclobenzaprine: If concomitant use warranted, monitor for serotonin syndrome, particularly during initiation of therapy and dosage increases

If serotonin syndrome suspected, discontinue pentazocine, cyclobenzaprine, and/or any concurrently administered opiates or serotonergic agents

St. John’s wort (Hypericum perforatum)

Risk of serotonin syndrome

If concomitant use warranted, monitor for serotonin syndrome, particularly during initiation of therapy and dosage increases

If serotonin syndrome suspected, discontinue pentazocine, St. John’s wort, and/or any concurrently administered opiates or serotonergic agents

Tests for urinary 17-hydroxycorticosteroids

Possible decrease in urinary 17-hydroxycorticosteroid determinations (Porter-Silber reaction)

Clinical importance not established

Tryptophan

Risk of serotonin syndrome

If concomitant use warranted, monitor for serotonin syndrome, particularly during initiation of therapy and dosage increases

If serotonin syndrome suspected, discontinue pentazocine, tryptophan, and/or any concurrently administered opiates or serotonergic agents

Pentazocine Pharmacokinetics

Absorption

Bioavailability

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

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

Onset

Following oral administration, onset of analgesia occurs within 15–30 minutes; peak analgesia occurs within 1–3 hours.

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

Following IV administration, onset of analgesia occurs within 2–3 minutes; peak analgesia occurs within 15 minutes.

Duration

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

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

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.

Distribution

Extent

Widely distributed in the body.

Crosses the placenta; neonatal serum concentrations reported to average about 65% of maternal concentrations at delivery.

Not known whether pentazocine is distributed into milk.

Plasma Protein Binding

About 60%.

Elimination

Metabolism

Metabolized in the liver.

Elimination Route

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

Half-life

2–3 hours.

Special Populations

In patients with hepatic impairment, clearance may be decreased and elimination half-life prolonged.

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

Stability

Storage

Oral

Tablets

25°C (may be exposed to 15–30°C).

Actions

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

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

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

  • 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.

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.

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

  • 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. Importance of informing patients that pentazocine should not be combined with alcohol.

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

  • Potential risk of serotonin syndrome with concurrent use of pentazocine and other serotonergic agents. 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.

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

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

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

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

  • Importance of advising patients of other important precautionary information. (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

Pentazocine and Naloxone Hydrochlorides

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

Tablets

Pentazocine Hydrochloride 50 mg (of pentazocine) and Naloxone Hydrochloride 0.5 mg (of naloxone)*

Pentazocine and Naloxone Hydrochlorides Tablets ( C-IV)

AHFS DI Essentials™. © Copyright 2022, Selected Revisions March 29, 2021. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

Show article references