Which antidote reverses opioids?

• A. Flumazenil
• B. Naloxone
• C. Yohimbine
• D. Atipamezole

Answer: (B)

Reversing opioid effects requires a receptor-specific antagonist that blocks mu opioid receptors, preventing opioids from activating them. Naloxone fits this role because it is a competitive antagonist at mu, kappa, and delta receptors with high affinity for the mu receptor, where most of the life-threatening opioid effects (analgesia, sedation, and especially respiratory depression) come from. By binding to these receptors, naloxone displaces any opioid molecules already attached and rapidly reverses the dangerous effects, often within minutes after administration.

An important practical point is that naloxone’s duration can be shorter than that of some opioids, so symptoms can reappear as the reversal wears off. This means repeated dosing or a continuous infusion may be needed and patients must be monitored closely for re-sedation or recurrence of respiratory depression.

Other agents listed don’t reverse opioids. Flumazenil targets benzodiazepine receptors, reversing benzodiazepine effects. Yohimbine and atipamezole reverse alpha-2 agonists (like xylazine or dexmedetomidine), not opioids, so they won’t counteract opioid-induced depression.