Which medication is used to treat serotonin syndrome?

• A. Diazepam
• B. Naloxone
• C. Physostigmine
• D. Cyproheptadine

Answer: (D)

Serotonin syndrome requires blocking the effects of excess serotonin. Cyproheptadine fits this need because it is a serotonin receptor antagonist, with strong action at the 5-HT2A receptors, which helps reverse the agitated state, neuromuscular hyperactivity, and hyperthermia seen in the condition. By blocking these receptors, cyproheptadine directly counters the underlying excess serotonergic activity, making it the most appropriate specific treatment among the options.

Diazepam can calm agitation and reduce tremors, but it doesn’t counteract serotonin’s effects on receptors; it provides supportive relief rather than addressing the root cause. Naloxone treats opioid toxicity, not serotonin toxicity. Physostigmine is used for anticholinergic toxicity, not serotonin syndrome. So, while supportive care (discontinuing the offending drug, fluids, cooling, and benzodiazepines as needed) is important, cyproheptadine specifically targets and mitigates the serotonergic excess, which is why it is the best choice.