A patient with schizophrenia is stabilized on clozapine 450 mg/day. His absolute neutrophil count (ANC) drops to 900 cells/mm³ on routine monitoring. According to REMS protocol, the next step is:

• A Continue clozapine and repeat ANC in 4 weeks
• B Reduce clozapine dose by 50% and monitor weekly
• C Permanently discontinue clozapine and start haloperidol
• D Interrupt clozapine immediately; monitor daily until ANC ≥1000; rechallenge with precautions ✓

Explanation

Per Clozapine REMS (Risk Evaluation and Mitigation Strategy), an ANC of 500-999 cells/mm³ (severe neutropenia) requires immediate interruption of clozapine, daily ANC monitoring until recovery to ≥1000, and consideration of cautious rechallenge under specialist guidance. ANC <500 (agranulocytosis) requires permanent discontinuation. ANC 1000-1499 is mild neutropenia requiring twice-weekly monitoring but not necessarily interruption. This patient's ANC of 900 falls in the severe neutropenia category.

Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.

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Written and medically reviewed by the StethoPrep medical team.