Neutropenia and agranulocytosis in patients receiving clozapine in the UK and Ireland

Abstract

Background: Clozapine can cause reversible agranulocytosis and neutropenia. This study documents the occurrence of blood dyscrasias and identifies predisposing risk factors.

Method: An analysis was made of the haematological, demographic, and dosage data from a central database on 6316 patients receiving clozapine over four and a half years in the UK and Ireland.

Results: During the study period, 2.9% of the patients developed neutropenia and 0.8% developed agranulocytosis. The peak incidence of both disorders was in the first 6-18 weeks of treatment. Fatal agranulocytosis occurred in 0.03% of patients. After the first year of treatment, the incidence of agranulocytosis significantly decreased to the order noted with some phenothiazines.

Conclusions: The use of a patient monitoring service kept the haematological risks associated with using clozapine within acceptable limits, particularly in view of the benefits of this medication in treatment-resistant schizophrenia.