(763) Serotonin Syndrome: A Case of Tapentadol Association

Introduction: Tapentadol is a centrally acting analgesic with a dual mechanism of action, combining mu-opioid receptor agonism with norepinephrine reuptake inhibition. The potential for serotonin syndrome with the concomitant use of serotonergic antidepressants has been observed but infrequently documented. We present a unique case of serotonin syndrome induced by the combined use of tapentadol and trazodone.

Description: A 53-year-old male with a history of anxiety and depression, treated with trazodone, was found unresponsive in his car alongside an envelope containing over a hundred tablets of tapentadol. Upon arrival, he presented with a temperature of 39.7°C, blood pressure of 188/91 mmHg, agitation, and inducible clonus observed during the physical exam. The Poison Control Center was consulted, recommending intravenous fluids and lorazepam as needed. Despite multiple doses of lorazepam and external cooling measures, the patient remained persistently agitated and confused, with high-grade fevers. Given the high suspicion for serotonin syndrome, cyproheptadine was initiated, leading to an improvement in fever, clonus, and agitation, although mild confusion persisted. Magnetic resonance imaging of the brain revealed no acute changes, and a lumbar puncture showed normal opening pressure and cerebrospinal fluid analysis. Over the following day, the patient gradually returned to his baseline mentation. Once alert and oriented, he reported abusing tapentadol and alcohol for several weeks. After psychiatric evaluation, he was discharged to the inpatient psychiatric unit for substance abuse treatment.

Discussion: Serotonin syndrome is a rare but serious reaction that can occur when tapentadol is combined with serotonergic antidepressants, due to excessive stimulation of 5-HT1a and 5-HT2 receptors. Symptoms include fever, autonomic dysregulation, clonus, tremor, and hyperreflexia. The Hunter Criteria, with 84% sensitivity and 97% specificity, is crucial for diagnosis. Management involves stopping the offending agent and providing supportive care. Cyproheptadine is recommended for those who remain symptomatic. This case highlights the necessity of recognizing serotonin syndrome in patients on tapentadol and serotonergic antidepressants showing the critical role of prompt treatment with cyproheptadine.