Opioid Substitution Formulations — MRCPsych Paper B MCQ

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ModerateSubstance MisuseOpioid Substitution FormulationsMRCPsych Paper B

A 28-year-old man with opioid dependence and a history of injecting heroin asks why buprenorphine is sometimes prescribed with naloxone as a sublingual combination (Suboxone). What is the main clinical rationale for including naloxone?

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Correct answer: B — It deters intravenous misuse of the sublingual preparation

The correct answer is B. Naloxone is included principally to deter misuse of the sublingual buprenorphine preparation by injection. When the combination is taken as directed, naloxone has relatively low sublingual absorption and little clinically significant antagonist effect. If the preparation is crushed and injected, naloxone becomes systemically available and antagonises opioid effects; in an opioid-dependent person it may precipitate withdrawal and make injection less rewarding. This is a deterrent rather than an absolute safeguard against misuse. Naloxone does not enhance analgesia or buprenorphine bioavailability, and it does not reliably prevent respiratory depression during prescribed use. It is also not included to reduce opioid-induced constipation.

Reference: Office for Health Improvement and Disparities, Part 1: introducing opioid substitution treatment (OST), section 1.3, 2021. https://www.gov.uk/government/publications/opioid-substitution-treatment-guide-for-keyworkers/part-1-introducing-opioid-substitution-treatment-ost