Long-acting injectable antipsychotics (LAI-APs) remain underutilized. One reason is the concern that LAI-APs might cause serious adverse events such as neuroleptic malignant syndrome (NMS) and lead to prolonged symptoms compared with oral treatment. Because the risk of NMS associated with LAI second-generation antipsychotics (LAI-SGAs) remains unclear, we compared reporting frequency, time to onset, and mortality of NMS between LAI- and oral SGAs using data from a Japanese spontaneous adverse event reporting database between April 2004 and September 2019. Of 5791 patients reporting adverse events due to LAI-SGAs or the equivalent oral SGAs, 768 (13%) developed NMS. LAI aripiprazole and LAI paliperidone were associated with a significantly lower reporting frequency of NMS than the equivalent oral SGAs (adjusted reporting odds ratio [95% confidence interval]: 0.35 [0.19–0.63] and 0.40 [0.27–0.59], respectively). Between 42% and 62% of the NMS associated with LAI- and oral SGAs other than LAI risperidone occurred within 30 days after initiation. The proportion of mortality due to NMS associated with oral aripiprazole was 13.1% and no deaths occurred in patients with NMS associated with LAI aripiprazole. The proportions of mortality due to NMS associated with oral risperidone/paliperidone, LAI risperidone, and LAI paliperidone were 8.8%, 4.2%, and 3.4%, respectively. Our findings showed that LAI-SGAs were not associated with a higher reporting frequency and mortality of NMS compared with oral SGAs, although clinicians need to closely monitor the occurrence of NMS not only during oral SGA treatment, but also, and in particular, in the early stage of LAI-SGA treatment.
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