Prevalence and Correlates of Serotonin Syndrome in Real-World Inpatients

Serotonin syndrome (SS) is a potentially life-threatening adverse drug reaction due to an increased central and peripheral serotonin activity, which usually presents as a triad of behavioral changes, neuromuscular excitability, and autonomic instability. Probably SS is often misdiagnosed, and its symptoms are mistaken for psychiatric symptoms or general medical issues: the true incidence of SS is not clear, and literature concerning potential risk factors is scarce. Our aims were to examine the prevalence of SS in a naturalistic sample of hospitalized patients and to evaluate potential factors related to the risk of developing the condition.

The sample included 133 patients being treated with serotonergic medications admitted to the psychiatric inpatient unit of the San Luigi Gonzaga Hospital. All patients received a medical examination (including a neurological examination) within 24 hours of admission. Serotonin syndrome was diagnosed according to Hunter Criteria.

Sixteen patients (12%) were diagnosed with SS. In the subgroup of subjects with SS, we found a higher rate of male patients when compared with subjects with no SS (62.5% vs 33.3%, P = 0.023).

SS probably is an underestimated condition, which should be carefully assessed in patients on serotonergic medications. Male gender was the only factor found to be significantly related to a higher risk of developing SS. Further studies on larger samples are needed, to gain more information on possible risk factors and to identify subjects more prone to developing SS, given the potential risk for patients' health.