Venous Thromboembolism Following Dantrolene Treatment for Neuroleptic Malignant Syndrome

Neuroleptic malignant syndrome (NMS) is one of the most severe iatrogenic emergencies in clinical service. The symptoms including sudden consciousness change, critical temperature elevation and electrolytes imbalance followed by mutli-organ system failure were common in NMS. In addition to aggressive interventions with intravenous fluid resuscitation and antipyretics, several antidotes have been suggested to prevent further progression of the muscle damage. Dantrolene has been reported to be one of the most effective treatments for NMS. However, the adverse effects of dantrolene treatment for NMS have not yet been evaluated thoroughly. Here we report a young male patient with bipolar I disorder who developed NMS after rapid tranquilization with haloperidol. Dantrolene was given intravenously for the treatment of NMS. However, fever accompanied with local tenderness, hardness with clear border and swelling with heat over the patient's left forearm occurred on the sixth day of dantrolene treatment. Venous thromboembolism (VTE) over intravenous indwelling site at the patient's forearm was noted and confirmed by Doppler ultrasound. The patient's VTE recovered after heparin and warfarin thrombolytic therapy. To our knowledge, this is the first case report demonstrating the possible relationship between dantrolene use and VTE in a patient with antipsychotic treatment. Although the causal relationship and the underlying pathogenesis require further studies, dantrolene should be used with caution for patients with NMS.