High risk of eosinophilia in women treated with clozapine

Eosinophilia associated with clozapine treatment has been reported in some studies and limited case reports. Because little is known regarding incidence, course, and relevance of this finding, clozapine therapy has been terminated prematurely in some patients with elevated eosinophil counts.

Records were reviewed on 118 consecutively hospitalized, acutely psychotic patients treated over a 1-year period with clozapine for at least 3 weeks. Demographic data were obtained on those patients, and white blood cell counts were analyzed. We reviewed the data for predisposing factors, associated medical findings, or clinical sequelae, and performed a two-sided Fisher's exact test to determine if sex or diagnosis was associated with a higher risk of developing eosinophilia. The literature pertaining to this blood dyscrasia and its relationship to clozapine was reviewed.

In our population, the cumulative incidence of eosinophilia among women was 23% (13/57), a statistically significant higher risk (p < .01) than that in men (7% [4/61]). In all cases, the eosinophilia was noted between Weeks 3 and 5 of treatment and resolved without medical or psychiatric complications.

Eosinophilia should be added to the list of commonly observed side effects of clozapine treatment. Women appear to be at significant risk. Eosinophilia usually occurs early in therapy, spontaneously resolves, and is not associated with any known complications. An otherwise healthy person with this blood dyscrasia may continue with treatment but should be monitored closely. Further investigation into this finding may provide insight into the mechanism of neutropenia and other adverse reactions to clozapine.