TALWIN 50
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TALWIN 50 (TALWIN 50).
Pentazocine is a mixed agonist-antagonist opioid analgesic with activity at kappa opioid receptors (agonist) and mu opioid receptors (partial agonist/antagonist). It also exhibits weak antagonistic activity at mu receptors, which reduces abuse liability but may precipitate withdrawal in opioid-dependent patients.
| Metabolism | Primarily hepatic via CYP3A4 and CYP2C19; also undergoes glucuronidation. Metabolites include hydroxylated and conjugated forms, which are excreted renally. |
| Excretion | Primarily renal (60-70% as unchanged drug and conjugates), with 20-30% biliary/fecal elimination. Approximately 5-10% excreted in feces via bile. |
| Half-life | Terminal elimination half-life is 2-3 hours. In patients with hepatic impairment, half-life may extend to 5-8 hours; in renal impairment, minimal change, but active metabolite accumulation may occur. |
| Protein binding | Approximately 60% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | 5-8 L/kg, indicating extensive tissue distribution and high accumulation in tissues (e.g., liver, kidney, lungs). |
| Bioavailability | Oral: 17-20% due to first-pass metabolism; Intramuscular/Subcutaneous: >90%. |
| Onset of Action | Intramuscular: 15-30 minutes; Subcutaneous: 20-40 minutes; Oral: 30-60 minutes. |
| Duration of Action | Intramuscular: 2-3 hours; Subcutaneous: 2-3 hours; Oral: 3-4 hours. Duration may be extended with higher doses or in hepatic impairment. |
50 mg orally every 3-4 hours as needed; maximum 600 mg per day.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: 50 mg every 6 hours; GFR 10-29 mL/min: 50 mg every 8 hours; GFR <10 mL/min: 50 mg every 12 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 25%; Child-Pugh C: reduce dose by 50% or avoid use. |
| Pediatric use | Not recommended for pediatric use due to safety concerns. |
| Geriatric use | Initiate at 25 mg every 4 hours and titrate cautiously; monitor for respiratory depression and constipation. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TALWIN 50 (TALWIN 50).
| Breastfeeding | Excreted in breast milk in low concentrations. M/P ratio not established. Use with caution; monitor infant for sedation and respiratory depression. |
| Teratogenic Risk | First trimester: Limited human data; animal studies show no evidence of teratogenicity. Second and third trimesters: Prolonged use may cause neonatal opioid withdrawal syndrome; avoid near term as respiratory depression may occur. |
| Fetal Monitoring |
■ FDA Black Box Warning
Risk of serious or fatal respiratory depression, particularly in elderly or debilitated patients; risk of addiction, abuse, and misuse; accidental ingestion may cause fatal overdose especially in children; neonatal opioid withdrawal syndrome with prolonged use during pregnancy; risks from concomitant use with CNS depressants (e.g., benzodiazepines) that may lead to profound sedation, respiratory depression, coma, and death.
| Serious Effects |
Significant respiratory depression; acute or severe bronchial asthma; known or suspected gastrointestinal obstruction (e.g., paralytic ileus); hypersensitivity to pentazocine or any component of the formulation; concurrent use of MAOIs or within 14 days of MAOI cessation; in patients who are physically dependent on opioids and are not in a controlled treatment setting (risk of precipitated withdrawal).
| Precautions | Respiratory depression; opioid-induced hyperalgesia; hypotension; increased intracranial pressure; seizure risk; biliary spasm; severe injection site reactions (e.g., induration, fibrosis, necrosis); risk of withdrawal in opioid-dependent patients; adrenal insufficiency; severe hypotension; impaired mental/physical abilities; caution in renal/hepatic impairment; avoid in pregnancy unless benefit outweighs risk; not recommended for children under 12 years. |
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| Monitor maternal respiratory rate, sedation level, and pain control. Assess neonatal for signs of opioid withdrawal if used chronically. Consider fetal heart rate monitoring during labor if TALWIN is administered. |
| Fertility Effects | No adequate human studies; animal studies do not suggest impaired fertility at therapeutic doses. |