What is the mechanism of action of naloxone?

Naloxone primarily functions as an opioid antagonist. Its key mechanism of action involves binding to opioid receptors in the central nervous system, particularly the mu-opioid receptor, where it competes with and displaces opioid agonists. This competitive inhibition results in the reversal of opioid effects, such as respiratory depression and sedation caused by opioid overdose.

This action allows naloxone to quickly restore normal respiration in individuals who have overdosed on opioids. While it does not have agonistic effects like full agonist opioids do, it is indeed categorized in the mixed agonist/antagonist class because, in certain contexts and at specific receptors, it can act as an antagonist while other drugs in this category may have partial agonist properties.

The other choices provide different classes of drugs that do not match naloxone's mechanism. Full agonist opioids would activate the receptor fully rather than blocking it. Selective serotonin reuptake inhibitors have no role in opioid receptor activity. Non-selective beta antagonists target beta-adrenergic receptors rather than opioid receptors and have no relation to opioid action. Hence, naloxone's defined role as a mixed agonist/antagonist in the context of opioid receptor binding solidifies its unique pharmac