Which of the following is an example of an opioid antagonist?

Which of the following is an example of an opioid antagonist?

• A. Naloxone
• B. Morphine
• C. Fentanyl
• D. Buprenorphine

Answer: (A)

An opioid antagonist is a drug that binds to opioid receptors without activating them, effectively blocking or reversing the effects of opioids. Naloxone fits this role perfectly: it has high affinity for mu receptors and competes with opioid agonists, displacing them and reversing opioid-induced respiratory depression and sedation. That makes it the classic example of an opioid antagonist. Morphine and fentanyl are opioid agonists; they activate mu receptors to produce analgesia plus side effects like respiratory depression. Buprenorphine is a partial agonist with high receptor affinity, so it activates the receptor but only partially, and it can block other opioids from acting, but it is not a pure antagonist.

An opioid antagonist is a drug that binds to opioid receptors without activating them, effectively blocking or reversing the effects of opioids. Naloxone fits this role perfectly: it has high affinity for mu receptors and competes with opioid agonists, displacing them and reversing opioid-induced respiratory depression and sedation. That makes it the classic example of an opioid antagonist.

Morphine and fentanyl are opioid agonists; they activate mu receptors to produce analgesia plus side effects like respiratory depression. Buprenorphine is a partial agonist with high receptor affinity, so it activates the receptor but only partially, and it can block other opioids from acting, but it is not a pure antagonist.