Serotonin syndrome vs neuroleptic malignant syndrome: a contrast of causes, diagnoses, and management.

Background: Serotonin syndrome (SS) and neuroleptic malignant syndrome (NMS) are uncommon but potentially life-threatening adverse reactions associated with psychotropic medications. Polypharmacy and the similar presentation of SS and NMS make diagnosis of the 2 syndromes problematic.
Methods: A MEDLINE search was performed for the period 1960 to 2011 for case reports, review articles, and studies pertaining to SS and NMS.
Results: The majority of available literature on SS and NMS consists of case reports, case-control studies, and retrospective reviews. In addition, diagnostic criteria have been developed to aid in the diagnosis and management of SS and NMS.
Conclusions: SS presents as mental status changes, autonomic nervous system disturbances, neurologic manifestations, and hyperthermia. Similarly, NMS presents as muscle rigidity, hyperpyrexia, mental status changes, and autonomic instability. However, the clinical laboratory profile of elevations in creatine kinase, liver function tests (lactate dehydrogenase, aspartate transaminase), and white blood cell count, coupled with a low serum iron level, distinguishes NMS from SS among patients taking neuroleptic and serotonin agonist medications simultaneously. For both SS and NMS, immediate discontinuation of the causative agent is the primary treatment, along with supportive care. For NMS, dantrolene is the most effective evidence-based drug treatment whereas there are no evidence-based drug treatments for SS. A 2-week washout of neuroleptic medication minimizes the chance of recurrence.