Which statement describes the mechanism of action of naloxone in reversing opioid overdoses?

• A. It binds to the serum opioids to prevent absorption into the brain
• B. It antagonizes opioid effects by occupying the same receptor sites
• C. It stimulates the respiratory center of the brain
• D. It antagonizes opioid effects by competing for the same receptor sites

Answer: (D)

Naloxone works by competitively blocking opioid receptors, especially the mu receptors, which are responsible for most of the opioid-induced respiratory depression. It binds to these receptors with high affinity and displaces any opioid molecules already occupying them. By occupying the receptor sites, it prevents opioids from activating the receptors, reversing the central nervous system and respiratory depression without producing opioid effects itself. It’s important to note that it acts at the receptor level rather than removing opioids from the blood or stimulating respiration directly. Because naloxone’s effects wear off sooner than many opioids, patients can relapse as the opioid outlasts the antidote, so additional dosing or infusion may be needed.