Section 19 · Monograph
Naloxone
Reviewed Nov 2026FDA label
Narcan / Evzio / ZimhiOpioid antagonist
- Forms
- Nasal: 4mg | Inj: 0.4mg/mL | Auto-injector: 5mg (Zimhi)
- Dose
- Opioid overdose: 4mg intranasal repeated every 2-3 min, or 0.4-2mg IV/IM/SC every 2-3 min; titrate small doses (0.04mg) for opioid-induced respiratory depression in palliative care
- MOA
- Competitive μ-opioid receptor antagonism
Indications
- Emergency treatment of known or suspected opioid overdose with respiratory and/or CNS depressionFDA-labeled
- Reversal of opioid effects including respiratory depression (injection)FDA-labeled
Mechanism of Action
- Competitive mu-opioid receptor antagonist that rapidly reverses opioid effects
Full Dosing
Adult / usual
- Overdose: 4mg intranasal into one nostril, repeat every 2-3 minutes with alternating nostrils as needed; or 0.4-2mg IV/IM/SC every 2-3 minutes
- Palliative or hospital opioid-induced respiratory depression: titrate in small increments (about 0.04mg IV) to restore respiration without causing severe pain or withdrawal
- Short duration (30-90 minutes) versus long-acting or high-dose opioids: monitor for renarcotization and repeat as needed; call emergency services after nasal use
Contraindications
- Hypersensitivity to naloxone
Drug Interactions
- Reverses analgesia and can precipitate acute withdrawal in opioid-dependent patients
- Partial agonists (buprenorphine) may require higher or repeated doses
Adverse Effects
- Acute opioid withdrawal (agitation, vomiting, tachycardia, hypertension)
- Recurrence of pain
- Pulmonary edema and arrhythmias (rare)
Monitoring Parameters
- Respiratory rate and consciousness for at least several hours
- Vital signs and recurrence of sedation
- Pain control after reversal
Pregnancy & Lactation
- Use if benefit outweighs risk; can induce fetal withdrawal in opioid-dependent mothers
- Compatible with breastfeeding