Atypical Neuroleptic Malignant Syndrome Associated With Olanzapine

Atypical Neuroleptic Malignant Syndrome Associated With Olanzapine

Roy R. Reeves, D.O., Ph.D., Raphael A. Torres, M.D., Vincent Liberto, M.D., Roy H. Hart, M.D.

Abstract

Neuroleptic malignant syndrome (NMS) is a potentially life-threatening adverse effect of antipsychotic agents. It generally is characterized by fever, altered mental status, rigidity, and autonomic dysfunction. A 53-year-old man developed NMS without rigidity while taking olanzapine. Such atypical cases may support either a spectrum concept of NMS or the theory that NMS secondary to atypical antipsychotics differs from that caused by conventional neuroleptics. More flexible diagnostic criteria than currently mandated by the the Diagnostic and Statistical Manual of Mental Disorders, Fourth Revision, may be warranted.

Introduction

Neuroleptic malignant syndrome (NMS) is an uncommon side effect of antipsychotic drugs, usually characterized by fever, altered mental status, rigidity, and autonomic dysfunction. The pathophysiology of NMS is not fully understood. Reduction in dopaminergic activity secondary to neuroleptic-induced dopamine blockade is considered the chief mechanism. This syndrome was first described in 1960 during clinical trials with haloperidol. Since that time, NMS has been associated with virtually all dopamine-blocking agents. Because many atypical antipsychotic agents have weaker dopamine blockade and lower rates of extrapyramidal side effects than conventional antipsychotic agents, it has been suggested that atypical antipsychotic agents are less likely to cause NMS. However, this remains unproven, and cases of NMS associated with clozapine, risperidone, olanzapine, and quetiapine have been reported...

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