A review of clozapine: an antipsychotic for treatment-resistant schizophrenia.

This report reviews over 25 years of literature of the development, pharmacology, proposed mechanism of action, efficacy, adverse effects, and recommendations for use of clozapine. Clozapine, synthesized in 1960, is an efficacious antipsychotic that rarely causes extrapyramidal side effects. However, in the mid-1970s, it was associated with an increased incidence of agranulocytosis resulting in restrictions of use. Recent trials with treatment-resistant schizophrenic patients found clozapine to be superior to chlorpromazine and haloperidol, fortifying the potential contribution of this drug. This has generated optimism that clozapine will obtain Food and Drug Administration approval. Generally well tolerated, the 1% to 2% risk of agranulocytosis can be minimized with careful patient selection, white blood cell (WBC) count monitoring, and weighing of risks versus benefits for use beyond the relatively safe initial 4-week period.