Mortality of Neuroleptic Malignant Syndrome Induced by Typical and Atypical Antipsychotic Drugs

Abstract

Neuroleptic malignant syndrome induced by atypical antipsychotics presents atypical clinical manifestations with fewer symptoms compared with neuroleptic malignant syndrome induced by typical antipsychotics. However, any differences in prognosis between these 2 types of drug-induced neuroleptic malignant syndrome remain unknown. We examined neuroleptic malignant syndrome-related mortality in patients treated with typical or atypical antipsychotics by using a national administrative claims database. Data of patients with a diagnosis of neuroleptic malignant syndrome between July and December in each of the 5 years from 2004 to 2008 were extracted from the Japanese Diagnosis Procedure Combination database. Data included patient background, use of antipsychotics, and in-hospital mortality. Propensity score matching was performed to formulate a balanced 1:1 matched study and to compare in-hospital mortality between neuroleptic malignant syndrome patients taking typical antipsychotics and those taking atypical antipsychotics. We identified 423 neuroleptic malignant syndrome patients treated with typical antipsychotics and 215 neuroleptic malignant syndrome patients treated with atypical antipsychotics. Matching based on propensity scores produced 210 patients in each drug group. In-hospital mortality was substantially lower in the atypical antipsychotic group compared with the typical antipsychotic group, but the difference was not significant (3.3% vs 7.6%; OR = 0.44; 95% CI, 0.17-1.11; P = .084). The results show that neuroleptic malignant syndrome remains a life threatening disease among patients receiving antipsychotics. A tendency for lower mortality in the atypical antipsychotic group may reflect differences in the pathophysiology. However, to clarify whether there is a difference in neuroleptic malignant syndrome-related mortality with the 2 types of antipsychotics, further studies with larger samples are needed.