Opioid antagonist

  • 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
  • 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

Pharmacology 101

Top 200 drugs

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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