How it's calculated
Adult dosing is a fixed 0.4-2 mg IV/IM/SC (or 4 mg intranasal), repeated every 2-3 minutes as needed. Paediatric dosing is weight-based at 0.1 mg/kg. Patients with suspected chronic opioid dependence start at a much lower dose to reverse respiratory depression while minimising precipitated withdrawal.
Dosing summary
| Population | Starting dose |
|---|---|
| Adult, opioid-naive | 0.4-2 mg IV/IM/SC, or 4 mg intranasal |
| Adult, suspected dependence | 0.04-0.4 mg IV/IM/SC, titrate |
| Paediatric | 0.1 mg/kg IV/IM/SC |
Clinical use
- First-line reversal agent for suspected opioid overdose with respiratory depression.
- Its duration of action (roughly 30-90 minutes) is often shorter than the opioid being reversed, especially long-acting or extended-release formulations — patients need monitoring for re-sedation and may need repeat dosing or an infusion.
- In known or suspected opioid-dependent patients, starting low and titrating reduces the risk of precipitating acute, severe withdrawal while still reversing life-threatening respiratory depression.
Frequently asked questions
Why start with a lower dose in opioid-dependent patients?
A full reversal dose can precipitate acute, severe opioid withdrawal in a dependent patient — uncomfortable, and can itself cause agitation and vomiting with aspiration risk. Titrating from a lower dose aims to restore adequate breathing without fully reversing all opioid effects.
How often can naloxone be repeated?
Every 2-3 minutes as needed, since it may take several doses to achieve adequate reversal, up to a total of around 10 mg in the classic dosing guidance — though real-world practice varies with the potency of the opioid involved (e.g. fentanyl analogues may need more).
Does naloxone work on all overdoses?
No — it specifically reverses opioid effects and has no effect on overdoses from other sedatives (e.g. benzodiazepines) or stimulants. If there's no response to an adequate naloxone dose, consider other causes of altered consciousness.
References
- Narcan (naloxone) Prescribing Information.
- American Heart Association. ACLS Provider Manual — Toxicology.