TALWIN NX

Clinical safety rating: caution

Comprehensive clinical and safety monograph for TALWIN NX (TALWIN NX).

How it works

Pentazocine is a mixed agonist-antagonist opioid analgesic that acts as an agonist at kappa opioid receptors and as an antagonist or partial agonist at mu opioid receptors. Naloxone is added to prevent intravenous abuse but has no oral bioavailability.

What the body does with it

Metabolism	Primarily hepatic via conjugation and oxidative pathways; CYP3A4 and CYP2C19 are involved in N-demethylation.
Excretion	Renal: ~60% as unchanged drug and glucuronide conjugates. Biliary/fecal: ~20% as metabolites. Total: 80% eliminated within 72 hours.
Half-life	2-3 hours (terminal) for pentazocine; naloxone half-life 1-1.5 hours. Clinically, duration limited by pentazocine's shorter half-life.
Protein binding	Pentazocine: ~60% bound to albumin. Naloxone: ~45% bound to plasma proteins.
Volume of Distribution	Pentazocine: 5-7 L/kg; indicates extensive tissue distribution. Naloxone: 2.5-3 L/kg.
Bioavailability	Oral: ~20% (due to extensive first-pass metabolism). Parenteral: 100% (IV/IM).
Onset of Action	Oral: 15-30 minutes; IM: 15-20 minutes; IV: 2-3 minutes.
Duration of Action	Oral: 3-4 hours; IM/IV: 2-3 hours. Note: Naloxone component reduces abuse potential but does not prolong analgesia.

Classification & Brands

Dosing & administration

1 tablet (pentazocine 50 mg/naloxone 0.5 mg) orally every 3-4 hours as needed for pain; maximum 12 tablets per day.

Dosage form	TABLET
Renal impairment	For GFR 30-50 mL/min: administer every 4-6 hours. For GFR 10-29 mL/min: administer every 6-8 hours. For GFR <10 mL/min: administer every 8-12 hours.
Liver impairment	Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce dose by 50% and extend dosing interval to every 6 hours. Child-Pugh Class C: avoid use.
Pediatric use	Not recommended for use in pediatric patients; safety and efficacy not established.
Geriatric use	Start with half of the usual adult dose (0.5 tablet) every 4-6 hours; titrate cautiously due to increased sensitivity and risk of respiratory depression and urinary retention.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for TALWIN NX (TALWIN NX).

Breastfeeding	Excreted into breast milk; M/P ratio not established. Limited data suggest low levels, but risk of infant sedation and respiratory depression. Caution advised; consider risk versus benefit.
Teratogenic Risk	FDA Pregnancy Category C. First trimester: Limited human data; animal studies show increased risk of skeletal anomalies and fetal resorption. Second/third trimester: Chronic use may cause neonatal opioid withdrawal syndrome (NOWS), respiratory depression, and low birth weight. High doses near term can lead to neonatal respiratory depression.

Warnings & precautions

■ FDA Black Box Warning

Concomitant use with alcohol or CNS depressants may cause severe respiratory depression. Risk of respiratory depression, abuse, and misuse. Accidental ingestion can be fatal, especially in children.

Side Effect Profile

Serious Effects

Absolute Contraindications

Hypersensitivity to pentazocine or naloxone; significant respiratory depression; acute or severe bronchial asthma; known or suspected gastrointestinal obstruction (including paralytic ileus); concomitant use with MAO inhibitors or within 14 days.

Clinical Precautions

Precautions

Respiratory depression; drug dependence and abuse potential; neonatal withdrawal syndrome with prolonged use; severe hypotension; increased intracranial pressure; risks of serotonin syndrome when used with serotonergic drugs; severe injection site reactions (including necrosis) with repeated intramuscular or subcutaneous administration.

Clinical Tips & Counseling

Drug interactions

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TALWIN NX

Clinical safety rating: caution

Comprehensive clinical and safety monograph for TALWIN NX (TALWIN NX).

How it works

What the body does with it

Metabolism	Primarily hepatic via conjugation and oxidative pathways; CYP3A4 and CYP2C19 are involved in N-demethylation.
Excretion	Renal: ~60% as unchanged drug and glucuronide conjugates. Biliary/fecal: ~20% as metabolites. Total: 80% eliminated within 72 hours.
Half-life	2-3 hours (terminal) for pentazocine; naloxone half-life 1-1.5 hours. Clinically, duration limited by pentazocine's shorter half-life.
Protein binding	Pentazocine: ~60% bound to albumin. Naloxone: ~45% bound to plasma proteins.
Volume of Distribution	Pentazocine: 5-7 L/kg; indicates extensive tissue distribution. Naloxone: 2.5-3 L/kg.
Bioavailability	Oral: ~20% (due to extensive first-pass metabolism). Parenteral: 100% (IV/IM).
Onset of Action	Oral: 15-30 minutes; IM: 15-20 minutes; IV: 2-3 minutes.
Duration of Action	Oral: 3-4 hours; IM/IV: 2-3 hours. Note: Naloxone component reduces abuse potential but does not prolong analgesia.

Classification & Brands

Dosing & administration

1 tablet (pentazocine 50 mg/naloxone 0.5 mg) orally every 3-4 hours as needed for pain; maximum 12 tablets per day.

Dosage form	TABLET
Renal impairment	For GFR 30-50 mL/min: administer every 4-6 hours. For GFR 10-29 mL/min: administer every 6-8 hours. For GFR <10 mL/min: administer every 8-12 hours.
Liver impairment	Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce dose by 50% and extend dosing interval to every 6 hours. Child-Pugh Class C: avoid use.
Pediatric use	Not recommended for use in pediatric patients; safety and efficacy not established.
Geriatric use	Start with half of the usual adult dose (0.5 tablet) every 4-6 hours; titrate cautiously due to increased sensitivity and risk of respiratory depression and urinary retention.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for TALWIN NX (TALWIN NX).

Breastfeeding	Excreted into breast milk; M/P ratio not established. Limited data suggest low levels, but risk of infant sedation and respiratory depression. Caution advised; consider risk versus benefit.
Teratogenic Risk	FDA Pregnancy Category C. First trimester: Limited human data; animal studies show increased risk of skeletal anomalies and fetal resorption. Second/third trimester: Chronic use may cause neonatal opioid withdrawal syndrome (NOWS), respiratory depression, and low birth weight. High doses near term can lead to neonatal respiratory depression.

Warnings & precautions

■ FDA Black Box Warning

Concomitant use with alcohol or CNS depressants may cause severe respiratory depression. Risk of respiratory depression, abuse, and misuse. Accidental ingestion can be fatal, especially in children.