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Opioid Substitution — MRCPsych Paper B MCQ

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HardSubstance MisuseOpioid SubstitutionMRCPsych Paper B

A 32-year-old man with opioid dependence has been clinically stable on supervised methadone 80 mg daily for 2 years. He wishes to change to buprenorphine. A standard licensed sublingual induction, rather than a low-dose overlap or micro-induction regimen, is planned. Which transfer sequence is most appropriate?

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Reveal the answer and explanation

Correct answer: E — Taper methadone to 30 mg/day or less, wait at least 24 hours after the final dose, and start buprenorphine only when objective withdrawal is present

Explanation lettering: C = shown as A · E = shown as B · D = shown as C · B = shown as D · A = shown as E

Option A is correct. For standard sublingual transfer, methadone should first be reduced to no more than 30 mg/day. After the final methadone dose, buprenorphine should not be administered for at least 24 hours and should be started only when objective, clear withdrawal is present; some patients require a longer interval. Buprenorphine has high mu-opioid-receptor affinity but only partial agonist activity, so giving it while substantial full-agonist activity remains can precipitate withdrawal. Direct transfer from 80 mg (C) is therefore unsuitable for standard induction. A fixed 12-hour interval or starting before withdrawal (B) is unsafe. Reduction only to 60 mg and induction irrespective of symptoms (D) retains the same risk. Seven days of abstinence (E) is unnecessary and may increase disengagement, relapse and overdose risk.

Reference: Buprenorphine 2 mg Sublingual tablets (Morningside Healthcare Ltd). Summary of Product Characteristics, sections 4.2 and 4.4, eMC current version. https://www.medicines.org.uk/emc/product/101115/smpc