Which antiemetic agents are commonly used for PONV prophylaxis?

• A. Dexamethasone and ondansetron
• B. Diphenhydramine
• C. Epinephrine
• D. Morphine

Answer: (A)

Postoperative nausea and vomiting prophylaxis relies on using antiemetics that work through different mechanisms to block multiple emetic pathways. Dexamethasone provides a strong antiemetic effect with anti-inflammatory actions and a long duration, making it a reliable foundation. Ondansetron, a 5-HT3 receptor antagonist, directly blocks serotonin signals in both the gut and chemoreceptor trigger zone, effectively reducing nausea from surgical stimuli and opioids. Using these two together gives additive protection and is a common approach, especially for patients at higher risk of PONV. Practical dosing often includes giving dexamethasone at induction and ondansetron toward the end of surgery. In contrast, diphenhydramine has antiemetic effects but is not as effective as a primary prophylaxis; epinephrine has no antiemetic role; and morphine can worsen PONV.