A patient receiving cisplatin-based chemotherapy is protected from vomiting on day 1 by palonosetron plus dexamethasone, but still experiences nausea on days 2 and 3. Which agent specifically targets the mediator responsible for this delayed phase?
- A Aprepitant ✓
- B Metoclopramide
- C Scopolamine
- D Lorazepam
Correct answer: A. Aprepitant
Explanation
The delayed phase of chemotherapy-induced emesis, occurring beyond 24 hours, is driven largely by substance P acting at neurokinin-1 receptors in the nucleus tractus solitarius and area postrema. Aprepitant is a selective NK-1 receptor antagonist that blocks this pathway and is combined with a 5-HT3 antagonist and dexamethasone in highly emetogenic regimens. Metoclopramide was historically used for delayed emesis but has a narrower therapeutic index and more adverse effects.
Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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