NARCAN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NARCAN (NARCAN).
Opioid receptor antagonist; binds competitively to mu, kappa, and delta opioid receptors, reversing opioid effects.
| Metabolism | Primarily hepatic glucuronidation via UGT1A8 and UGT2B7 to naloxone-3-glucuronide; minimal CYP450 involvement. |
| Excretion | Primarily hepatic metabolism (glucuronidation) followed by renal excretion of metabolites; <5% excreted unchanged in urine. |
| Half-life | Approximately 1 hour in adults; context: shorter than most opioids (e.g., morphine 2-4 h), necessitating repeated doses for prolonged opioid effects. |
| Protein binding | Approximately 45-55% bound to serum proteins, primarily albumin. |
| Volume of Distribution | Approximately 1.0-1.5 L/kg; clinical meaning: extensive distribution outside plasma, indicating rapid tissue uptake. |
| Bioavailability | Intranasal: approximately 50% relative to intravenous; intramuscular/subcutaneous: approximately 50-100% due to first-pass metabolism. |
| Onset of Action | Intravenous: 1-2 minutes; intramuscular/subcutaneous: 2-5 minutes; intranasal: approximately 2-3 minutes. |
| Duration of Action | Approximately 30-90 minutes; clinical note: duration may be shorter than that of many opioids, requiring repeat dosing or continuous infusion. |
Initial dose: 0.4 mg to 2 mg IV, IM, or SC, repeated every 2 to 3 minutes as needed. For opioid-induced respiratory depression, may use 0.1 to 0.2 mg IV increments in patients with opioid dependence to avoid withdrawal.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required; naloxone is primarily metabolized by the liver and not significantly renally excreted. |
| Liver impairment | No specific dose adjustment; use with caution in severe hepatic impairment due to potential altered metabolism. |
| Pediatric use | 0.01-0.1 mg/kg IV, IM, or SC every 2-3 minutes as needed; maximum single dose 2 mg. For neonates: 0.01-0.1 mg/kg IV or IM, repeat every 2-3 minutes if needed. |
| Geriatric use | No specific dose adjustment; initiate at lower end of dosing range (0.1-0.2 mg) and titrate due to potential increased sensitivity and risk of withdrawal. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NARCAN (NARCAN).
| Breastfeeding | Naloxone is excreted into breast milk in very low amounts. The M/P ratio is not established. The half-life in breast milk is short, and the risk to the nursing infant is negligible. Use in breastfeeding mothers is considered acceptable when clinically indicated. |
| Teratogenic Risk | Naloxone (NARCAN) is not teratogenic in animal studies. Human data are limited, but no increased risk of major malformations has been reported. First trimester: No known teratogenic risk. Second/third trimester: No known fetal risks; naloxone crosses the placenta but has minimal fetal effects due to short half-life and lack of opioid agonist activity. |
■ FDA Black Box Warning
Risk of precipitating acute opioid withdrawal; monitor for recurrence of respiratory depression due to short duration of action.
| Serious Effects |
Hypersensitivity to naloxone or any component.
| Precautions | May precipitate acute withdrawal in opioid-dependent patients; repeated doses may be needed due to shorter half-life than many opioids; not effective for non-opioid overdoses. |
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| Fetal Monitoring | Monitor for recurrence of respiratory depression, blood pressure, heart rate, and oxygen saturation in the mother. Fetal monitoring includes heart rate and uterine activity if indicated (e.g., in opioid-dependent labor). No specific long-term monitoring required after reversal. |
| Fertility Effects | No known effects on fertility. Naloxone does not alter reproductive hormones or gamete function in animal studies. |