Comparison of neuroleptic malignant syndrome induced by first- and second-generation antipsychotics

Background: Reports of neuroleptic malignant syndrome (NMS) induced by second-generation antipsychotic drugs highlight a propensity for atypical clinical presentations. Aims: To systematically compare the clinical profile of NMS induced by first- (1G-NMS) and second-generation antipsychotic drugs (2G-NMS). Method: The Australian Adverse Drug Reaction Advisory Committee (ADRAC) database was searched to identify individuals with NMS reported between April 1994 and September 2010. The clinical characteristics of 208 people with NMS induced by monotherapy with first- or second-generation antipsychotic drugs, as well as presenting features of NMS, were compared. Results: The individuals with 2G-NMS were younger and more likely to have a psychotic disorder diagnosis. The features of NMS in the two groups were very similar, except that people with 2G-NMS were less likely to present with rigidity or extrapyramidal signs compared with those with 1G-NMS. This difference was due to the lower rates of rigidity in those with clozapine-induced NMS. Mortality was considerably lower for those with 2G-NMS (3.0%) compared with 1G-NMS (16.3%), and the former were more likely to have received supportive treatment. Conclusions: The clinical profile of 2G-NMS is largely similar to 1G-NMS, with clozapine-induced NMS being differentiated by the relative lack of rigidity as a feature. Mortality is lower for 2G-NMS.