Clozapine-Induced Agranulocytosis -- Incidence and Risk Factors in the United States

Abstract

Clozapine is an atypical antipsychotic agent that is more effective than standard neuroleptic drugs in the treatment of patients with refractory schizophrenia. Unlike classic neuroleptic agents, clozapine is not associated with the development of acute extrapyramidal symptoms or tardive dyskinesia. The main factor limiting its use is the risk of potentially fatal agranulocytosis, estimated to occur in 1 to 2 percent of treated patients. After clozapine was approved by the Food and Drug Administration, it became available for marketing in the United States in February 1990 only as part of a special surveillance system (the Clozaril Patient Management System, or CPMS), in which a weekly white-cell count was required for the patient to receive a supply of the drug.