Narcan (Naloxone) Dosing for Suspected Opioid Overdose
For adults with suspected opioid overdose, administer an initial intravenous dose of 0.4 to 2 mg naloxone, repeating every 2-3 minutes as needed, with lower starting doses (0.04 to 0.4 mg) reserved for known opioid-dependent patients to minimize withdrawal symptoms. 1
Initial Dose Selection
The FDA-approved initial dose range is 0.4 mg to 2 mg administered intravenously, with repeat dosing at 2-3 minute intervals if inadequate response occurs. 2 This recommendation is supported by the American Heart Association, which emphasizes titrating to effect rather than consciousness 1.
Dose Stratification Based on Patient Characteristics:
- Standard patients (no known opioid dependence): Start with 0.4 to 2 mg IV 1, 2
- Known opioid-dependent patients: Start with lower doses of 0.04 to 0.4 mg to avoid precipitating severe withdrawal syndrome, which can include hypertension, tachycardia, agitation, vomiting, and violent behavior 3, 1
- Pediatric patients: 0.01 mg/kg IV initially; if inadequate response, give 0.1 mg/kg 2
- Neonates: 0.01 mg/kg IV, IM, or subcutaneous 2
Route of Administration Priority
Intravenous administration is preferred because it provides the most rapid onset and allows for precise dose titration. 2, 4
Alternative Routes When IV Access Unavailable:
- Intramuscular: 2 mg, repeated in 3-5 minutes if necessary 1
- Intranasal: 2 mg (using higher-concentration 2 mg/mL formulations), repeated in 3-5 minutes if necessary 1, 5
- Note: Lower-concentration intranasal formulations (2 mg/5 mL) are less effective than intramuscular administration 5
- Subcutaneous: Same dosing as intramuscular 2
The intranasal route has approximately 50% bioavailability and slower uptake (mean time to maximum concentration 15-30 minutes) compared to intramuscular administration 6.
Critical Management Priorities
Airway management and bag-mask ventilation must take absolute priority before naloxone administration. 1 This is a common pitfall—providers should never delay standard resuscitation measures while waiting for naloxone to take effect 1.
Clinical Context Determines Approach:
- Respiratory arrest with pulse present: Provide bag-mask ventilation first, then administer naloxone alongside standard BLS/ACLS care 1
- Cardiac arrest: Focus on high-quality CPR; naloxone has no proven benefit in cardiac arrest and should not delay resuscitation 3, 1
Repeat Dosing Algorithm
If no response after initial dose, repeat or escalate to 2 mg every 2-3 minutes. 1, 2 If no response occurs after 10 mg total has been administered, question the diagnosis of opioid-induced toxicity 2.
Approximately 9% of patients require two or more doses of naloxone for clinical reversal, with 2% requiring three doses 7. Synthetic opioids like fentanyl may require higher total doses 6.
Duration of Action and Monitoring Requirements
Naloxone's duration of action is 45-70 minutes, which is often shorter than the respiratory depressant effects of many opioids. 3, 1 This creates a critical safety window requiring extended observation.
Observation Requirements:
- Short-acting opioids (heroin, morphine): Brief observation period may be appropriate 3
- Long-acting opioids (methadone, sustained-release formulations): Prolonged observation required until risk of recurrent toxicity is low and vital signs normalized 3, 1
- All patients: Monitor in healthcare setting; repeated small doses or continuous infusion may be needed if recurrent toxicity develops 1
Common Pitfalls to Avoid
Excessive naloxone dosing causes significant reversal of analgesia, hypertension, nausea, vomiting, sweating, agitation, and circulatory stress. 1 Use the lowest effective dose to minimize these effects 1.
Premature discharge after successful reversal is dangerous—recurrent respiratory depression is common. 1 No patient who achieved GCS 15 after treatment required redosing in one large study, but continued monitoring remains essential 7.
Naloxone will not reverse respiratory depression from non-opioid drugs such as benzodiazepines—recognize mixed overdoses and maintain ventilatory support regardless 1.
The intranasal route may have slower onset than intramuscular administration, so clinical response may lag behind other routes 6. Consider this when selecting route in critical situations.