Risk of neuroleptic malignant syndrome in patients with bipolar disorder: A retrospective, population-based case-control study

Introduction: Current data regarding risk factors of neuroleptic malignant syndrome (NMS) are limited. This study aims to examine factors associated with increased risk of NMS in patients with bipolar disorder. Methods: A retrospective, population-based, case-control study was performed using a medical claims database covering January 1998 to December 2002. Fifty cases with a diagnosis of NMS were identified and matched with 800 controls. Conditional logistic regression analysis was used to estimate crude and adjusted odds ratios (ORs) of risk of NMS. Results: Antipsychotic use was associated with an increased risk of NMS after controlling for other pharmacologic and clinical factors (OR = 2.36, 95% CI = 1.08-5.19). Other factors associated with an increased risk of NMS included being male (OR = 2.07, 95% CI = 1.07-4.02), confusion (OR = 2.91, 95% CI = 1.17-7.28), dehydration (OR = 3.99, 95% CI = 1.50-10.57), delirium (OR = 4.93, 95% CI = 2.07-11.72), and extrapyramidal symptoms (OR = 3.50, 95% CI = 1.10-11.09). Conclusions: Given the widespread use of antipsychotics for the treatment of bipolar disorder, clinicians should be vigilant of the potential pharmacologic and clinical factors associated with increased risk of NMS in patients with bipolar disorder.