Naltrexone — MRCPsych Paper B MCQ
Instant feedback + full explanation. One question, done properly.
Educational content. Not a substitute for clinical judgement or local policy.
Reveal the answer and explanation
Correct answer: D — Naltrexone
Explanation lettering: C = shown as B · E = shown as C · B = shown as D · D = shown as E
Naltrexone (B) is correct. It is a non-selective competitive opioid receptor antagonist: by blocking opioid receptors it attenuates endogenous opioid-mediated reward from drinking, reducing the motivation to drink and the risk that a lapse becomes a full relapse. Note it blocks receptors rather than preventing endogenous opioid release. Acamprosate (A) is also used for relapse prevention but works via glutamatergic (NMDA) and GABAergic modulation, not opioid antagonism. Disulfiram (C) inhibits aldehyde dehydrogenase, causing an aversive acetaldehyde reaction with alcohol; it does not act on opioid receptors. Methadone (D) is a full mu-opioid receptor agonist and buprenorphine (E) a partial mu-opioid agonist (with kappa antagonism); both are opioid-substitution treatments for opioid dependence, not opioid antagonists used to reduce alcohol reward.
Reference: Office for Health Improvement and Disparities / DHSC. Clinical guidelines for alcohol treatment, Chapter 10: Pharmacological interventions (naltrexone). 2025. https://www.gov.uk/guidance/clinical-guidelines-for-alcohol-treatment/10-pharmacological-interventions