A 38-year-old woman awakens from anesthesia after cholecystectomy and experiences postoperative nausea and vomiting. Which is the appropriate treatment for her symptoms?

• A. Dimenhydrinate
• B. Metoclopramide
• C. Prochlorperazine
• D. Ondansetron

Answer: (D)

Postoperative nausea and vomiting are best treated with an antiemetic that is highly effective for anesthesia-related triggers and has a low risk of extrapyramidal symptoms. Ondansetron is a 5-HT3 receptor antagonist that blocks serotonin receptors both in the gut and in the vomiting center of the brain, which directly reduces the nausea and the reflex pathways driving vomiting after surgery. This mechanism provides strong antiemetic effect with a favorable safety profile, making it a preferred choice in the immediate postoperative setting.

Other antiemetics work via different pathways. Dimenhydrinate is mainly an antihistamine with some anticholinergic effects, which can help motion sickness but is generally less effective for PONV and can cause drowsiness. Metoclopramide and prochlorperazine are dopamine D2 receptor antagonists and can be effective, but they carry a higher risk of extrapyramidal symptoms and other side effects, which is less desirable right after anesthesia. Thus, ondansetron stands out for controlling postoperative nausea and vomiting with fewer motor side effects.

Note: monitor for QT prolongation in patients with preexisting conduction abnormalities or those on other QT-prolonging drugs, but in most postoperative patients, ondansetron provides the best balance of efficacy and safety.