Clozapine Agranulocytosis — RACP Adult Medicine MCQ

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EasyClinical PharmacologyClozapine AgranulocytosisRACP Adult Medicine

A 55-year-old man with schizophrenia on clozapine 400 mg daily presents with fever (38.9°C), tachycardia, and a sore throat. His WCC is 0.6 × 10⁹/L with an ANC of 0.1 × 10⁹/L. What is the most critical immediate action?

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Correct answer: B — Cease clozapine immediately and commence G-CSF

Clozapine-induced agranulocytosis (ANC <0.5 × 10⁹/L) is a medical emergency with a mortality rate of 3–4% without treatment. Clozapine must be IMMEDIATELY and PERMANENTLY ceased. G-CSF (filgrastim) should be commenced urgently. The patient should be managed as febrile neutropaenia with empirical broad-spectrum antibiotics. Regular blood monitoring (weekly for the first 18 weeks, then monthly) is mandated for all patients on clozapine. This patient must never receive clozapine again.

Reference: AMH – 2025 – Clozapine; eTG – 2025 – Psychotropic; TGA – 2024 – Clozapine Monitoring Requirements