A 30-year-old heroin addict is initiated on buprenorphine-naloxone for opioid use disorder. He receives his first dose 18 hours after his last heroin use. Why is naloxone included in the sublingual formulation?
- A To reverse opioid overdose during buprenorphine induction
- B Naloxone enhances buprenorphine analgesic potency
- C To prevent intravenous abuse — naloxone has poor sublingual bioavailability but if injected precipitates withdrawal ✓
- D To prevent buprenorphine from crossing the blood-brain barrier
Correct answer: C. To prevent intravenous abuse — naloxone has poor sublingual bioavailability but if injected precipitates withdrawal
Explanation
Naloxone is included as an abuse-deterrent. When the combined tablet is taken sublingually as prescribed, naloxone has negligible bioavailability (<10%) and produces no effect; buprenorphine acts normally. If a patient dissolves and injects the tablet, naloxone has high IV bioavailability and precipitates acute opioid withdrawal — deterring IV misuse. Buprenorphine itself as a partial agonist is unlikely to be diverted for IV use when naloxone is present.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
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