Naloxone is an opioid antagonist used for the treatment of opioid or heroin overdose. It is a fast-acting drug that binds to and blocks opioid receptors, reversing sedation and respiratory depression caused by opioids. However, its fast antagonism can cause some patients to go into acute withdrawal.

Key Points

  • Naloxone
    • Commonly referred to by trade name: Narcan
    • Mechanism
      • Opioid receptor antagonist
        • Has high affinity for receptors (displaces opioids) but no activity (antagonist)
        • Highest binding affinity to mu opioid receptors, although it also blocks delta and kappa opioid receptors
        • Acts within minutes
          • Contrast vs. Naltrexone, which acts slowly
    • Indications
      • Acute opioid intoxication
        • Usually in setting of overdose (especially heroin)
    • Adverse Effects
      • Opioid withdrawal
        • Sudden stopping of opioid signaling can lead to withdrawal symptoms and potentially cause seizures