Objective: Define the incidence of clozapine-induced leukopenia, neutropenia, and agranulocytosis in patients with schizophrenia at Srinagarind Hospital.
Material and Method: A descriptive study was done by retrospective reviews of the medical records of schizophrenic outpatients at psychiatric clinic in Srinagarind Hospital who had received clozapine from January 1st, 2003 to December 31st, 2005. The demographic data, incidence rate, and incidence density of leukopenia, neutropenia, and agranulocytosis were collected.
Results: One hundred and seventeen medical records were reviewed, 65 patients met the inclusion criteria. One patient developed neutropenia. The incidence rate of neutropenia was 1.5% and the incidence density of neutropenia was 0.01/year. No leukopenia or agranulocytosis was found in the present study. The complete blood counts were not obtained regularly due to the problems of patient’s adherence and variations in practice among the physicians.
Conclusion: Neutropenia is uncommon. No leukopenia and agranulocytosis were found. According to variations of incidence reports among different studies, the monitoring of white blood count should be continued.

Keywords: Clozapine, Leukopenia, Neutropenia, Agranulocytosis, Incidence rate, Incidence density