Which medication is a partial opioid agonist used in maintenance therapy?

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

Answer: (B)

Buprenorphine acts as a partial agonist at mu-opioid receptors, providing enough receptor activation to relieve withdrawal and cravings while introducing a ceiling effect that limits euphoria and respiratory depression. This balance makes it safer for long-term maintenance therapy in opioid use disorder. Methadone, by contrast, is a full agonist and carries a higher overdose risk despite also being used for maintenance. Naloxone and naltrexone are opioid antagonists—they block receptors rather than activate them—so they’re not used to sustain opioid effects in maintenance therapy. Often buprenorphine is given with naloxone in sublingual formulations to discourage misuse.