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Serotonin syndrome is a rare but potentially fatal adverse drug reaction associated with increased serotonergic activity in the central nervous system. It is characterized by a triad of symptoms, which include altered mental status, neuromuscular hyperactivity, and autonomic instability or hyperactivity. Due to the potential of rapid onset, it is important for clinicians to recognize the signs and symptoms of serotonin syndrome. Serotonin syndrome symptoms may resemble other conditions. Although this article focuses on serotonin syndrome as a result of an adverse interaction of selective serotonin reuptake inhibitors (SSRI) and fentanyl, it is important for not only anesthesia professionals, but all clinicians-such as those in emergency medicine and critical care-to be aware of this syndrome and its management. This article discusses the clinical manifestations of the serotonin syndrome and highlights reported cases of serotonin syndrome specifically related to an interaction between SSRIs and fentanyl, a commonly used opioid in anesthesia practice.
Keywords: Fentanyl, serotonin syndrome, serotonin toxicity, SSRI.
What Is Serotonin Syndrome?
Serotonin syndrome is a potentially fatal condition associated with increased serotonergic activity in the central nervous system that can be attributed to certain drugs, interactions between drugs, or intentional overdose.1 The terms serotonin toxicity and serotonin syndrome are often used interchangeably. Gillman reasons that the term serotonin toxicity is more accurate, as it reflects "the broad spectrum of serotoninrelated side effects progressing to toxicity."2,3 As serotonin syndrome is used predominantly in the literature and anesthesia-related texts, we will use the term serotonin syndrome throughout this article.
Serotonin syndrome is often characterized by a triad of symptoms, which include altered mental status, neuromuscular hyperactivity, and autonomic instability or hyperactivity. 4 The symptoms can range from mild to severe and can be fatal if leftuntreated.5 Table 1 provides a summary of mild, moderate, and severe symptoms associated with serotonin syndrome. Patients may be discharged following anesthesia with unrecognized symptoms of serotonin syndrome. After cessation of the drugs responsible for this syndrome, symptoms usually abate within 24 hours. However, in severe cases, it can take up to several days for symptoms to abate.6
What Causes Serotonin Syndrome?
A large number of drugs with serotonergic activity have been implicated in serotonin syndrome (see Table 2). Antidepressants known as serotonin reuptake inhibitors (SSRIs) are most commonly...