A patient with schizophrenia on clozapine develops absolute neutrophil count (ANC) of 480/mm³ on routine blood monitoring. According to current REMS protocols, the immediate action is:
- A Reduce clozapine dose by 50% and recheck CBC in 1 week
- B Interrupt clozapine therapy and monitor ANC daily until it recovers to >1000/mm³ ✓
- C Add G-CSF and continue clozapine at the same dose
- D Continue clozapine as this is mild neutropenia and re-check in 2 weeks
Explanation
An ANC <500/mm³ constitutes severe neutropenia (agranulocytosis threshold) requiring immediate interruption of clozapine therapy — the risk of potentially fatal agranulocytosis is not acceptable at this count. Per the clozapine REMS (Risk Evaluation and Mitigation Strategy) protocol: ANC 500–999/mm³ = mild/moderate neutropenia requiring more frequent monitoring; ANC <500/mm³ = immediate discontinuation, daily CBC monitoring, haematology consultation. G-CSF (filgrastim) may be used as adjunct therapy once clozapine is stopped, but never as a reason to continue the drug. Clozapine causes agranulocytosis in ~1–2% of patients, which is why mandatory haematological monitoring is a regulatory requirement.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
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Written and medically reviewed by the StethoPrep medical team.