Pentazocine

• Moderate to severe pain:
  Treatment of moderate to severe acute or chronic pain where use of an opioid analgesic is appropriate.
• Preoperative analgesia and anesthesia adjunct:
  Used as an analgesic before and during surgery or diagnostic procedures.
• Off-label uses:
  Occasionally used for labor pain and in some cases of obstetric analgesia.

• Route: Intramuscular (IM), intravenous (IV), subcutaneous (SC), or oral administration.
• Adults:
• Oral: Initial dose 50 mg every 3–4 hours as needed; maximum 600 mg/day.
• Parenteral (IM, SC, IV): 30 mg every 3–4 hours as needed; maximum 360 mg/day.
• Elderly:
  Start at lower doses with careful monitoring due to increased sensitivity and risk of respiratory depression.
• Pediatrics:
  Safety and efficacy not established; use with caution and under specialist supervision.
• Renal/Hepatic Impairment:
  Use with caution; dose adjustment may be necessary due to altered metabolism and clearance.

Pentazocine is a mixed opioid agonist-antagonist. It primarily acts as an agonist at kappa-opioid receptors producing analgesia and sedation, and as a partial agonist or antagonist at mu-opioid receptors, which limits typical opioid adverse effects such as respiratory depression and euphoria. This receptor activity profile results in effective pain relief with a lower risk of dependence compared to pure mu-opioid agonists.

• Absorption: Rapidly absorbed after oral administration; bioavailability approximately 60%.
• Distribution: Widely distributed; crosses the blood-brain barrier.
• Metabolism: Extensively metabolized in the liver via N-demethylation and conjugation.
• Half-life: Approximately 2–3 hours.
• Elimination: Mainly excreted in urine as metabolites; minor fecal excretion.

• Pregnancy: Category C (FDA). Animal studies show adverse effects on fetus; use only if potential benefits justify risks.
• Lactation: Excreted in breast milk; caution advised. Monitor nursing infants for sedation and respiratory depression.

• Opioid analgesic
• Mixed opioid agonist-antagonist

• Hypersensitivity to pentazocine or formulation excipients.
• Severe respiratory depression or respiratory insufficiency.
• Acute or severe asthma.
• Known or suspected gastrointestinal obstruction, including paralytic ileus.
• Use with caution in patients with head injury or increased intracranial pressure.

• Risk of respiratory depression, especially when combined with CNS depressants.
• Potential for dependence and abuse, although lower than pure mu-opioid agonists.
• Monitor for serotonin syndrome when used with serotonergic drugs.
• Avoid use in patients with significant cardiovascular disease; may cause tachycardia and hypertension.
• Caution in elderly and debilitated patients due to increased sensitivity.
• Use with caution in hepatic or renal impairment; monitor liver and kidney function.

• Common: Dizziness, nausea, vomiting, sweating, dry mouth, sedation, headache.
• Serious: Respiratory depression, hallucinations, confusion, tachycardia, hypotension, dependency, withdrawal symptoms.
• Side effects typically dose-dependent and may appear within hours of administration.

• CNS depressants (e.g., benzodiazepines, alcohol): Increased sedation and respiratory depression risk.
• Monoamine oxidase inhibitors (MAOIs): Risk of severe reactions including hypertension and CNS toxicity; avoid concomitant use.
• Serotonergic drugs: Potential serotonin syndrome.
• Other opioids: May precipitate withdrawal symptoms due to antagonist activity.

• Increased emphasis on careful patient selection to minimize abuse potential.
• Updated guidelines recommend cautious use in combination with other CNS depressants.
• No significant changes in approved indications or dosing.
• Ongoing evaluation of safety profile in special populations.

• Store at 20°C to 25°C (68°F to 77°F).
• Protect from light and moisture.
• Keep container tightly closed.
• Keep out of reach of children.