A patient on sertraline plus tramadol presents with agitation, clonus, hyperreflexia and diarrhoea. Alongside supportive care and benzodiazepines, which antidote is used for moderate to severe serotonin syndrome?
- A Cyproheptadine ✓
- B Naloxone
- C Flumazenil
- D Physostigmine
Correct answer: A. Cyproheptadine
Explanation
Serotonin syndrome reflects excessive serotonergic activity at central 5-HT1B and 5-HT2B receptors. Cyproheptadine is a first-generation antihistamine with potent 5-HT2B antagonism and is the standard antidote given orally or by nasogastric tube. Physostigmine was used historically but worsens cholinergic features such as diarrhoea and is no longer recommended, which is the point that dismisses option D. Benzodiazepines remain first line for mild cases.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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