A 35-year-old man with treatment-resistant schizophrenia is started on clozapine. After 3 months, he develops neutropenia. The hematological monitoring protocol requires weekly CBCs for:

• A The first 18 weeks of therapy
• B The entire duration of therapy
• C The first 4 weeks only
• D The first 6 months, then monthly thereafter ✓

Explanation

Current clozapine monitoring guidelines recommend weekly complete blood counts (CBC) for the first 18 weeks (approximately 4.5 months), then fortnightly for 1 year, then monthly thereafter—as long as the patient remains on the drug. Clozapine causes potentially fatal agranulocytosis in 0.5–2% of patients, predominantly within the first 3–6 months. The ANC threshold for stopping clozapine is below 1500/mm³ (mild-moderate neutropenia) or below 500/mm³ (agranulocytosis). Frequent early monitoring is critical to detect this serious adverse effect promptly.

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

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