Clinical Research Directory

Time Course of Clozapine-associated Agranulocytosis Over 19 Years

Clozapine is the most effective antipsychotic medication for treatment-resistant schizophrenia, but it carries a rare, potentially life-threatening risk of agranulocytosis (a severe drop in white blood cells), which is why patients undergo regular blood monitoring. Most cases occur in the first months of treatment, and it remains unclear how much risk persists after the first year. This retrospective study will use existing electronic health records from Sheba Medical Center (February 2007 to August 2026) to describe when agranulocytosis occurs among approximately 2,020 patients treated with clozapine over up to 19 years of follow-up. The study will estimate the cumulative incidence and incidence rates across follow-up periods, examine whether risk after the first 18 weeks remains stable over time, and assess age, sex and psychiatric diagnosis as predictors. Each case will be individually reviewed to distinguish clozapine-related events from neutropenia due to cancer or chemotherapy. No patients will be contacted and no treatment will be changed. The findings are intended to inform policy on long-term hematological monitoring of clozapine-treated patients.