To the Editor: Neuroleptic malignant syndrome is a potentially lethal side effect of antipsychotic medication. It may occur in as many as 1% to 2% of patients treated with antipsychotic medication +(1). Operational criteria include 1) fever (oral temperature greater than 37.5°C on two occasions); 2) extrapyramidal features, including one of a) moderately severe rigidity; b) at least two of mild rigidity, dysphagia, shuffling gait, resting tremor, dystonia, dyskinesia, and a creatinine kinase level greater than 400 U/liter; or c) a creatinine kinase level greater than 1000 U/liter; and 3) either a) altered consciousness or catatonia or b) autonomic instability (two or more of hypertension, labile blood pressure, tachycardia, intense diaphoresis, incontinence, and tachypnea) +(2). Although most of the reported cases of neuroleptic malignant syndrome to date have been associated with the use of classical antipsychotics, both risperidone +(3) and clozapine +(4) have been implicated in the emergence of the syndrome. We report here the first case of neuroleptic malignant syndrome induced by the novel antipsychotic olanzapine that met these operational criteria.

One should be alert to this serious side effect associated with atypical antipsychotic medication, including olanzapine.