1. 2015;18;E27-E30Incidence of Serotonin Syndrome in Patients Treated with Fentanyl on Serotonergic Agents
   
   Padma Gulur, MD, Becky Tsui, MD, and Katharine M. Koury, BA.

BACKGROUND: There has been a recent surge in the literature highlighting the association of fentanyl as precipitating serotonin syndrome in patients on a serotonergic agent.

OBJECTIVE: The purpose of our study was to understand the incidence of serotonin syndrome in patients who receive fentanyl while on serotonergic agents.

STUDY DESIGN: This retrospective analysis was conducted from 2012 to 2013 after approval from the Institutional Review Board. We searched for all patients that had received a serotonergic agent and were admitted to the hospital during the study period. Next, we split these patients into 2 groups by placing all patients who had received fentanyl and a serotonergic agent into one group. We then searched for any of the Hunter Serotonin Toxicity Criteria in the records of patients that had received both fentanyl and a serotonergic agent. Further, we searched for all patients with serotonin syndrome mentioned in their records.

SETTING: This study was conducted at a 900 bed tertiary care academic center.

RESULTS: Over the 2 year study period, 112,045 patients were on a serotonergic agent, and 4,538 of these patients were treated with both fentanyl and a serotonergic agent. A search for Hunter’s Criteria through the records of the patients receiving both fentanyl and a serotonergic agent revealed 23 patients had been documented with some of these symptoms. On detailed chart review, only 4 [95% CI 1 – 10] of these patients truly met Hunter’s Criteria for serotonin syndrome. We then searched all admissions for a diagnosis code of serotonin syndrome during the study period. Five additional cases of serotonin syndrome were found, but none of these patients were treated with fentanyl.

LIMITATIONS: Some of the limitations of our study include that it represents a single institution, although it is a large academic center. An inherent limitation may be the under diagnosis of serotonin syndrome.

CONCLUSION: The incidence of serotonin syndrome in patients who receive both fentanyl and a serotonergic agent is low.