Which opioid agonist is a full agonist used in MAT?

• A. Naloxone
• B. Naltrexone
• C. Methadone
• D. Buprenorphine

Answer: (C)

A full agonist in this context means a medication that fully activates the mu-opioid receptor to produce opioid-like effects, which helps prevent withdrawal and cravings in opioid use disorder. Methadone is a long-acting mu-opioid receptor full agonist, chosen for MAT because its steady activation provides reliable relief from withdrawal and reduces illicit opioid use, often with good treatment retention when used under supervision.

Naloxone and naltrexone are antagonists; they block receptor activity and are used to reverse overdose or prevent relapse, not to sustain opioid effects. Buprenorphine is a partial agonist, activating the receptor but with a ceiling effect that lowers overdose risk.