A 45-year-old man with metastatic bronchial carcinoid develops severe flushing, diarrhoea and agitation unresponsive to octreotide. Which orally available agent acting on serotonin receptors is most appropriate to control his symptoms?
- A Cyproheptadine ✓
- B Ondansetron
- C Buspirone
- D Sumatriptan
Correct answer: A. Cyproheptadine
Explanation
Cyproheptadine is a first-generation antihistamine with potent 5-HT2 receptor antagonist activity, and blockade of 5-HT2 receptors controls flushing and diarrhoea in carcinoid syndrome refractory to somatostatin analogues. Ondansetron blocks 5-HT3 receptors and helps nausea but does not address 5-HT2 mediated vasomotor symptoms. Buspirone is a 5-HT1B partial agonist used for anxiety. Sumatriptan is a 5-HT1A/1D agonist that would be inappropriate and potentially harmful in serotonin excess states.
Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.
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