A patient on clozapine develops absolute neutrophil count (ANC) of 450 cells/µL at week 8. According to pharmacovigilance monitoring guidelines, what is the appropriate management?

• A Continue clozapine with daily blood count monitoring and supportive care
• B Immediately discontinue clozapine, administer G-CSF, and do not rechallenge
• C Switch to another atypical antipsychotic immediately; monitor ANC weekly for 4 weeks
• D Withhold clozapine and do not rechallenge; the patient must never receive clozapine again ✓

Explanation

Clozapine-induced agranulocytosis (ANC <500 cells/µL) is a life-threatening idiosyncratic adverse effect occurring in ~1% of patients. It is thought to involve reactive nitrenium ion formation from clozapine metabolism that triggers immune-mediated destruction of myeloid progenitors. When agranulocytosis is confirmed, clozapine must be permanently discontinued and the patient registered as contraindicated for rechallenge. G-CSF is sometimes used for recovery but does not alter the contraindication. All clozapine prescribers must enrol in mandatory haematological monitoring programs (weekly for 26 weeks, then fortnightly).

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.