Recognizing serotonin syndrome in the intensive care unit: a case report of serotonin syndrome in a patient taking amitriptyline, buprenorphine, pregabalin, and fentanyl.

Background: Despite its life-threatening nature, serotonin syndrome (SS) often eludes initial recognition and remains an underreported condition that can occur with the administration of serotonergic drugs alone or in combination with other medications known to increase levels of serotonin. The diagnosis of SS relies on clinical assessment, as laboratory tests and imaging studies cannot definitively confirm the condition. The majority of reported cases of SS involve polypharmacy rather than single-drug overdose. Diagnosing SS can be challenging for physicians, particularly in the intensive care unit (ICU) settings where patients often present with multiple comorbidities. Nevertheless, SS should be considered in the differential diagnosis, mainly when the treatment regimen includes multiple serotonergic medications. Case Description: We present a case of SS that developed in a patient following the administration of fentanyl. The patient had a medical history of opioid use disorder and was on buprenorphine, amitriptyline, and pregabalin. Symptoms indicative of SS appeared within four hours after fentanyl was administered and began to improve within six hours after cessation of the potential offending agents, with complete resolution occurring within 24 hours. Conclusions: Our case underscores the significance of conducting a thorough neurological examination and medication assessment for the prompt diagnosis of SS. Additionally, it examines the medications that could have potentially triggered the events described in this case.