A young man develops agitation, hyperthermia, clonus and diarrhoea after combining an SSRI with tramadol. Alongside benzodiazepines and cooling, an oral agent that acts as a non-selective serotonin receptor antagonist, particularly at 5-HT2A receptors, may be used. This drug is:
- A Ondansetron
- B Risperidone
- C Cyproheptadine ✓
- D Granisetron
Correct answer: C. Cyproheptadine
Explanation
Cyproheptadine is a first-generation antihistamine with potent 5-HT2A and 5-HT2B antagonist activity, and it is the conventional antidote used in moderate to severe serotonin syndrome when supportive measures are insufficient. Ondansetron and granisetron are selective 5-HT3 antagonists and have no role here. Risperidone blocks 5-HT2A but also dopamine receptors and can worsen hyperthermia through extrapyramidal effects, so it is not the standard choice.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
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