ABSTRACT Introduction Neuroleptic malignant syndrome (NMS) is a life‐threatening adverse reaction to antipsychotic medications. Dantrolene is commonly used to manage NMS; however, supportive evidence from large‐scale clinical studies remains limited. This study aimed to evaluate the clinical impact of early dantrolene administration in intensive care unit (ICU)‐admitted patients with NMS using a nationwide inpatient database in Japan. Methods A retrospective cohort study was conducted using the Japanese Diagnosis Procedure Combination database from April 2010 to March 2023. Patients aged ≥ 16 years diagnosed with NMS and admitted to the ICU were included. The exposure of interest was dantrolene administration within the first 2 days of admission. The primary outcome was in‐hospital mortality; secondary outcomes included ICU and hospital length of stay. Baseline adjustment between the dantrolene‐treated and untreated groups was performed using two methods: propensity score matching (PSM) and generalized linear mixed models (GLMMs). Results A total of 2234 patients met the inclusion criteria, including 1475 treated with dantrolene and 759 without. In both analyses, dantrolene use was associated with an increase in in‐hospital mortality (adjusted OR: 2.03, 95% CI: 1.16–3.54; p = 0.01 in GLMM, adjusted OR: 1.92, 95% CI: 1.17–3.24; p = 0.01 in PSM). Dantrolene was also associated with prolonged ICU stay (mean difference: 1.66, 95% CI: 1.05–2.26; p < 0.001 in GLMM and 2.03, 95% CI: 1.31–2.76; p < 0.001 in PSM) and hospital stay (mean difference: 6.85, 95% CI: 3.48–10.21; p < 0.001 in GLMM and 6.81 days, 95% CI: 3.46–10.16; p < 0.001 in PSM). Subgroup analyses stratified by age (< 65 vs. ≥ 65 years) yielded similar trends. Conclusions In the largest study of NMS to date, early initiation of dantrolene was associated with higher in‐hospital mortality and prolonged ICU/hospital stay. These findings suggest that routine use of dantrolene in NMS should be reevaluated.
Suekane et al. (Thu,) studied this question.