Background: Clozapine is known to induce neutropenia as well as agranulocytosis. Some cases of olanzapine- and risperidone-induced neutropenia and agranulocytosis have also been reported. We prospectively investigated schizophrenia patients treated with second generation antipsychotics with respect to alterations of white blood cell counts.
Methods: In an analysis of our drug monitoring program, we studied white blood cell counts in 104 patients receiving different second generation antipsychotics other than clozapine for at least six months and compared them with those of 28 patients receiving clozapine.
Results: We found neutropenia (neutrophils <2 000/microL) in the mixed group in 17.6% and in 11.8% of patients treated with clozapine during the first 6 months. There was no statistically significant difference between those groups with respect to the risk to develop neutropenia during the investigation period. There was no case of agranulocytosis. Neutropenia was transient in all patients. Eosinophilia occurred in some patients that developed neutropenia later on but had no significant predictive value.