Clozapine blood dyscrasia — MRCPsych Paper A MCQ

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EasyPsychopharmacologyClozapine blood dyscrasiaMRCPsych Paper A

A 31-year-old man with schizophrenia that has not responded to two adequate antipsychotic trials is started on clozapine. He undergoes mandatory regular monitoring of his white blood cell and absolute neutrophil counts. Which serious adverse effect is this haematological monitoring primarily intended to detect?

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Correct answer: A — Agranulocytosis

The correct answer is A, agranulocytosis. Clozapine can cause neutropenia that may progress to potentially fatal agranulocytosis. Mandatory white blood cell and absolute neutrophil count monitoring is therefore required to identify haematological toxicity and permit prompt intervention. Nephrogenic diabetes insipidus is classically associated with lithium. Irreversible sensorineural hearing loss is associated particularly with ototoxic medicines such as aminoglycosides. Pulmonary fibrosis is linked to medicines including bleomycin and amiodarone. Anticholinergic medicines can precipitate acute angle-closure glaucoma in susceptible patients, and clozapine has anticholinergic effects, but this is not the purpose of mandatory blood-count monitoring.

Reference: Electronic Medicines Compendium, Clozaril 200 mg Tablets, Summary of Product Characteristics, sections 4.4 (Agranulocytosis; WBC and ANC monitoring), updated 20 April 2026. https://www.medicines.org.uk/emc/product/102057/smpc