skip to main content

Clozapine Myocarditis — MRCPsych Paper B MCQ

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

HardSchizophrenia & PsychosisClozapine MyocarditisMRCPsych Paper B

A 29-year-old man with treatment-resistant schizophrenia commenced clozapine 4 weeks ago. A repeat full blood count confirms an eosinophil count of 3.5 × 10⁹/L. His neutrophil count is satisfactory, and he has no fever, rash, resting tachycardia, chest pain, dyspnoea or flu-like symptoms. What is the most appropriate immediate action?

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

Reveal the answer and explanation

Correct answer: D — Temporarily discontinue clozapine and monitor the eosinophil count

The correct answer is D. The eosinophil count is above the UK clozapine SmPC threshold of 3.0 × 10⁹/L, so clozapine should be temporarily discontinued. Treatment may be restarted after the count falls below 1.0 × 10⁹/L, with re-titration if the interruption exceeds 48 hours. Although early eosinophilia can accompany myocarditis, it is not a reliable predictor of carditis. The absence of tachycardia, chest pain, dyspnoea or flu-like symptoms makes myocarditis less clinically apparent, but the eosinophil threshold independently requires interruption. Therefore, cardiac investigations do not justify continuing clozapine as in B. Dose reduction or routine observation is insufficient above this threshold. Permanent discontinuation and substitution with a depot are unnecessary unless a serious organ-specific hypersensitivity reaction is established.

Reference: Clozapine Viatris 100 mg Tablets, Summary of Product Characteristics, section 4.4: Eosinophilia and Cardiovascular disorders, updated 13 March 2026. https://www.medicines.org.uk/emc/product/15498/smpc