fosaprepitant + ondansetron

Fosaprepitant + ondansetron is a **combination of two pharmaceutical agents** used for the prevention of acute and delayed **nausea and vomiting**, particularly associated with **chemotherapy** (chemotherapy-induced nausea and vomiting, CINV) and **postoperative nausea and vomiting** (PONV). **Fosaprepitant** is a water-soluble phosphorylated prodrug of aprepitant, which after intravenous administration is rapidly converted to aprepitant, a highly selective **neurokinin-1 (NK1) receptor antagonist**. It blocks the action of substance P at NK1 receptors in the central nervous system. **Ondansetron** is a **selective serotonin 5-HT3 receptor antagonist** that blocks serotonin peripherally on vagal nerve terminals and centrally in the chemoreceptor trigger zone, inhibiting the emetic reflex. The **combination exploits complementary mechanisms**, resulting in broader antiemetic efficacy. Used together, they help prevent both the acute (first 24 hours) and delayed phases (25–120 hours) of emesis, particularly in patients undergoing highly emetogenic chemotherapy or at high risk for PONV[1][2][3][4][5][7].