A 28-year-old heroin-dependent man is being considered for opioid substitution therapy (OST). He has previously failed three detoxification attempts. Which agent used in OST acts as a partial agonist at the mu-opioid receptor and reduces illicit opioid use with better safety profile than methadone in overdose?
- A Naltrexone
- B Naloxone
- C Loperamide
- D Buprenorphine ✓
Explanation
Buprenorphine is a partial agonist at the mu-opioid receptor and an antagonist at the kappa-opioid receptor. Its partial agonism means it has a 'ceiling effect' on respiratory depression, making it significantly safer in overdose than full agonists like methadone. It is sublingual and highly effective for opioid substitution therapy (OST). Buprenorphine/naloxone combination (Suboxone) is preferred over buprenorphine alone to deter diversion/intravenous misuse (naloxone precipitates withdrawal if injected). Naltrexone is an opioid antagonist used for relapse prevention after detoxification, not for substitution therapy.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
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