Which statement describes a typical characteristic of opioid antagonists?

Which statement describes a typical characteristic of opioid antagonists?

• A. They have high affinity for opioid receptors and displace agonists, then do not activate the receptor
• B. They block reuptake of endogenous opioids
• C. They are full agonists at the receptor
• D. They enhance activation of pure agonists

Answer: (A)

Opioid antagonists work by binding to opioid receptors with high affinity but having little to no intrinsic activity, so they displace any bound agonists and do not activate the receptor themselves. This competitive binding allows them to rapidly reverse opioid effects—such as analgesia and respiratory depression—by blocking receptor activation even in the presence of opioids. They don’t work by blocking reuptake, they’re not full agonists, and they don’t enhance activation of agonists; instead they effectively prevent activation by occupying the receptor and turning off the signal.

Opioid antagonists work by binding to opioid receptors with high affinity but having little to no intrinsic activity, so they displace any bound agonists and do not activate the receptor themselves. This competitive binding allows them to rapidly reverse opioid effects—such as analgesia and respiratory depression—by blocking receptor activation even in the presence of opioids. They don’t work by blocking reuptake, they’re not full agonists, and they don’t enhance activation of agonists; instead they effectively prevent activation by occupying the receptor and turning off the signal.