A 24-year-old woman with a history of major depressive disorder treated with sertraline is brought to the emergency department by her partner for evaluation of fever, vomiting, and weakness. In the emergency department, her temperature is 103°F, her heart rate is 129 beats per minute, she is agitated and restless, and she displays hyperactive reflexes. Her symptoms began several hours after she used a new medication prescribed by her primary care provider. Which of the following is most likely to be the new medication?

Choice A reason: Propranolol is a beta-blocker used for anxiety, hypertension, and migraine prophylaxis. It does not increase serotonin levels and is not associated with serotonin syndrome, making it an unlikely cause of the described symptoms. Choice B reason: Topiramate is an anticonvulsant and mood stabilizer used for epilepsy and migraine prevention. It does not significantly affect serotonin pathways and is not known to cause serotonin syndrome. Choice C reason: Sumatriptan is a serotonin receptor agonist used for acute migraine treatment. When combined with SSRIs like sertraline, it can precipitate serotonin syndrome—a potentially life-threatening condition characterized by hyperthermia, autonomic instability, neuromuscular abnormalities, and altered mental status. The timing and symptoms strongly suggest this interaction. Choice D reason: Naproxen is a nonsteroidal anti-inflammatory drug (NSAID) used for pain and inflammation. It does not interact with serotonergic systems and is not associated with serotonin syndrome.