Episode 939: Serotonin Syndrome

Contributor: Jorge Chalit-Hernandez, OMS3 Educational Pearls: Serotonin syndrome occurs most commonly due to the combination of monoamine oxidase inhibition with concomitant serotonergic medications like SSRIs Examples of unexpected monoamine oxidase inhibitors Linezolid - a last-line antibiotic reserved for patients with true anaphylaxis to penicillins and cephalosporins Methylene blue - not mentioned in the podcast due to its uncommon usage for methemoglobinemia Other medications that can interact with SSRIs to cause serotonin syndrome Dextromethorphan - primarily an anti-tussive at sigma opioid receptors that also has serotonin reuptake inhibition Clinical presentation of serotonin syndrome Altered mental status Autonomic dysregulation leading to hypertension (most common), hypotension, and tachycardia Hyperthermia Neuromuscular hyperactivity - tremors, myoclonus, and hyperreflexia Hunter Criteria (high sensitivity and specificity for serotonin syndrome): Spontaneous clonus Inducible clonus + agitation or diaphoresis Ocular clonus + agitation or diaphoresis Tremor + hyperreflexia Hypertonia, temperature > 38º C, and ocular or inducible clonus Management of serotonin syndrome Primarily supportive - benzodiazepines can help treat hypertension, agitation, and hyperthermia. Patients often require repeated and higher dosing of benzodiazepines Avoid antipyretics to treat hyperthermia since the elevated temperature is due to sustained muscle contraction and not central temperature dysregulation In refractory patients, cyproheptadine (a 5HT2 antagonist) may be used as a second-line treatment Patients with temperatures > 41.1º C or 106º F require medically induced paralysis and intubation to control their temperature References Boyer EW, Shannon M. The serotonin syndrome [published correction appears in N Engl J Med. 2007 Jun 7;356(23):2437] [published correction appears in N Engl J Med. 2009 Oct 22;361(17):1714]. N Engl J Med. 2005;352(11):1112-1120. doi:10.1056/NEJMra041867 Dunkley EJ, Isbister GK, Sibbritt D, Dawson AH, Whyte IM. The Hunter Serotonin Toxicity Criteria: simple and accurate diagnostic decision rules for serotonin toxicity. QJM. 2003;96(9):635-642. doi:10.1093/qjmed/hcg109 Ramsay RR, Dunford C, Gillman PK. Methylene blue and serotonin toxicity: inhibition of monoamine oxidase A (MAO A) confirms a theoretical prediction. Br J Pharmacol. 2007;152(6):946-951. doi:10.1038/sj.bjp.0707430 Schwartz AR, Pizon AF, Brooks DE. Dextromethorphan-induced serotonin syndrome. Clin Toxicol (Phila). 2008;46(8):771-773. doi:10.1080/15563650701668625 Thomas CR, Rosenberg M, Blythe V, Meyer WJ 3rd. Serotonin syndrome and linezolid. J Am Acad Child Adolesc Psychiatry. 2004;43(7):790. doi:10.1097/01.chi.0000128830.13997.aa Summarized & Edited by Jorge Chalit, OMS3 Donate: https://emergencymedicalminute.org/donate/