Serotonin Syndrome — MRCPsych Paper B MCQ

Instant feedback + full explanation. One question, done properly.

ModerateLiaison PsychiatrySerotonin SyndromeMRCPsych Paper B

A 35-year-old man takes fluoxetine for depression and has been receiving a stable dose of olanzapine for several months. Twelve hours after tramadol is started for acute back pain, he develops agitation, diaphoresis and a temperature of 38.5°C. Examination shows dilated pupils, generalised hyperreflexia and inducible ankle clonus. Which syndrome is the most likely diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — Serotonin syndrome

The correct answer is D, serotonin syndrome. Tramadol has serotonergic activity, and its addition to fluoxetine provides the precipitating interaction. Rapid onset, agitation, diaphoresis, hyperthermia, hyperreflexia and particularly inducible clonus are characteristic; inducible clonus with agitation or diaphoresis satisfies the Hunter criteria in a patient exposed to serotonergic drugs. Neuroleptic malignant syndrome remains a relevant distractor because he takes olanzapine, but it more typically evolves over days with generalised rigidity and hyporeflexia rather than prominent clonus and hyperreflexia. Catatonia may cause psychomotor and autonomic abnormalities but does not explain this neuromuscular excitation following a serotonergic interaction. Acute dystonia causes sustained focal or generalised muscle contractions, while delirium alone does not account for clonus and hyperreflexia. Initial management is withdrawal of serotonergic agents and supportive care.

Reference: Tees, Esk and Wear Valleys NHS Foundation Trust. Medication Safety Series MSS 36: Serotonin Syndrome, Hunter Serotonin Toxicity Criteria, approved 2025. https://www.tewv.nhs.uk/wp-content/uploads/2025/10/MSS36-v1-Serotonin-Syndrome.pdf