[A case of neutropenia and agranulocytosis induced by clozapine. The importance of a drug surveillance program for their early detection].

Clozapine is an atypical antipsychotic drug with a very low incidence of extrapyramidal effects, used in the treatment of schizophrenic patients refractory or intolerant to classical neuroleptics. Its use is limited due to the potential risk of producing agranulocytosis in 1 to 2% of patients. Despite the severity of this complication, the Federal Drug Administration allowed its use as long as its prescription is associated to a drug surveillance program that controls regularly the white cell count of patients using the drug. Three hundred three patients (210 male) have been admitted to a clozapine drug surveillance program. Two patients had a transitory leukopenia with less than 2000 leukocytes/ml and less than 1000 neutrophyls/ml, that reverted after discontinuing the drug. One patient, whose case is described, had a severe agranulocytosis with less than 500 neutrophyls/ml that required hospital admission.