A 55-year-old woman receiving cisplatin-based chemotherapy is troubled mainly by nausea and vomiting occurring more than 24 hours after each cycle, despite ondansetron cover. The most appropriate addition targeting this delayed phase is:

• A Metoclopramide at antiemetic doses, a D2 antagonist
• B Scopolamine, a muscarinic antagonist
• C Promethazine, an H1 antihistamine
• D Aprepitant, a neurokinin-1 receptor antagonist ✓

Explanation

Delayed chemotherapy-induced nausea and vomiting beyond 24 hours is driven substantially by substance P acting at neurokinin-1 receptors in the vomiting center and area postrema. Aprepitant blocks NK-1 receptors and, with its long half-life, covers the delayed phase when added to a 5-HT3 antagonist plus dexamethasone. Scopolamine and promethazine suit motion sickness and vestibular causes, while metoclopramide adds little beyond existing serotonin blockade.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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