Predictive Value of Eosinophilia for Neutropenia During Clozapine Treatment

Background: Myelotoxicity continues to hinder the widespread use of clozapine in the United States. It has been theorized that eosinophilia predicts later agranulocytosis and that agranulocytosis occurs due to an immunologic mechanism. Our study compares the rates of these dyscrasias in clozapine-treated patients and a control group.

Method: Forty-one patients taking clozapine and 29 patients taking haloperidol were monitored for a period of 6 months. Rates of eosinophilia and neutropenia were compared between the two treatment groups.

Results: Treatment-emergent eosinophilia occurred frequently in both haloperidol- and clozapine- treated patients. No significant difference was seen between groups in the incidence of eosinophilia and neutropenia.

Conclusion: We find no statistical difference between the rates of eosinophilia or neutropenia in haloperidol- and clozapine-treated patients. This study does not support the use of eosinophilia as a reliable predictor of neutropenia.