Pharm 101: Naloxone
Class
Opioid antagonist
Pharmacodynamics
- Pure opioid antagonist that binds to mu-opioid binding sites
- Very high affinity for mu receptors, lower affinity for other receptor binding sites
- No tolerance to antagonist action
Pharmacokinetics
- IV administration:
- Reverses opioid toxicity in 1-3 minutes
- Duration of action 1-2 hours
- Rapid first pass metabolism
Clinical uses
- Life-threatening respiratory and CNS depression in opioid toxicity:
- Initial dose 0.1-0.4 mg
- Maintenance dose 0.4-0.8 mg, repeated as necessary
- Withdrawal after chronic administration does not precipitate an abstinence syndrome
Adverse effects
- Opioid withdrawal: precipitates abstinence syndrome in dependent users
- Resedation (short duration of action)
- Severely depressed patient may recover after a single dose and appear normal, and then relapse into coma after 1-2 hours
- Ways to avoid: smaller/titrated doses, infusion, route of administration
References
- Katzung BG. Basic and Clinical Pharmacology. 14e. 2018: 570-572
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Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Co-creator of the LITFL ECG Library. Twitter: @rob_buttner