TALWIN 50
Clinical safety rating
cautionComprehensive 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. |
| Molecular Weight | 285.38 |
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 | Avoid; associated with neural tube defects and cardiac malformations if exposure occurs in the first trimester. |
| 2nd trimester | Use only if clearly needed; risk of spontaneous abortion and fetal growth restriction. |
| 3rd trimester | Avoid; may cause neonatal respiratory depression, withdrawal syndrome, and neonatal opioid withdrawal syndrome (NOWS) if used near term. |
Clinical note
Comprehensive clinical and safety monograph for TALWIN 50 (TALWIN 50).
| Placental transfer | Pentazocine crosses the placenta; detectable in fetal tissues. Rapid placental transfer occurs, and fetal blood levels may approach maternal levels. |
| Breastfeeding | Pentazocine is excreted into breast milk in low concentrations. However, use during breastfeeding is not recommended due to potential for infant sedation, respiratory depression, and withdrawal. If use is necessary, monitor infant for drowsiness, poor feeding, and weight gain. |
| Lactation Rating | L4 (Possibly Hazardous) |
| 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 | 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. |
■ 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 |
Hypersensitivity to pentazocine or any componentPatients with acute or severe bronchial asthmaRespiratory depression in the absence of resuscitative equipmentSuspected or known gastrointestinal obstruction (e.g., paralytic ileus)Use of monoamine oxidase inhibitors (MAOIs) within 14 days
| 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. |
| Food/Dietary | No specific food interactions have been reported. Avoid alcohol consumption due to additive CNS depression. Grapefruit juice may inhibit metabolism of pentazocine (theoretical), but clinical significance is unclear. Maintain a balanced diet; no restrictions necessary. |
| Clinical Pearls | Talwin (pentazocine) is a mixed agonist-antagonist opioid analgesic. It can precipitate withdrawal in opioid-dependent patients due to its partial antagonist activity at mu receptors. Monitor for respiratory depression, which may not be fully reversed by naloxone. Avoid in patients with acute MI or coronary insufficiency as it can increase cardiac workload. Use with caution in renal impairment as accumulation of active metabolites may occur. |
| Patient Advice | Do not take Talwin if you have been using other opioids (e.g., morphine, codeine) as it can cause severe withdrawal symptoms. · This medication may cause dizziness, drowsiness, or blurred vision. Avoid driving or operating machinery until you know how it affects you. · Do not consume alcohol while taking Talwin as it increases the risk of severe sedation and respiratory depression. · Take Talwin exactly as prescribed. Do not increase dose or frequency without consulting your doctor. · If you are pregnant, planning to become pregnant, or breastfeeding, discuss with your doctor before use. · Store Talwin at room temperature away from moisture and heat. Keep out of reach of children. · Do not share this medication with others. It is a controlled substance and can cause dependence. |
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