Which antiemetic and route is recommended for nausea or vomiting?

• A. Ondansetron (Zofran) 4 mg IV or orally.
• B. Metoclopramide 10 mg IV.
• C. Dimenhydrinate 50 mg IV.
• D. Diphenhydramine 25 mg PO.

Answer: (A)

The best approach for rapid and effective relief of nausea or vomiting is using a selective serotonin 5-HT3 receptor antagonist that can be given either IV for quick action or orally for convenience. Ondansetron fits this well: it blocks serotonin receptors in both the gut and the brain’s chemoreceptor trigger zone, which helps stop nausea from a variety of causes, including postoperative and chemotherapy-related cases. The 4 mg dose is a standard, effective amount that works promptly when given IV or by mouth, providing flexibility depending on the clinical setting.

Compared with other options, metoclopramide can be effective but carries a higher risk of movement disorders due to dopamine blockade, which makes it less ideal for some patients. Dimenhydrinate and diphenhydramine are older antihistamines that can help but are generally less potent and more sedating, so they’re not the preferred first-line choice in many acute scenarios.