What is administered for nausea or vomiting and at what dose?

• A. Ondansetron (Zofran) 4 mg IV or orally.
• B. Diphenhydramine 25 mg PO.
• C. Metoclopramide 10 mg IV.
• D. Prochlorperazine 5 mg IV.

Answer: (A)

The main concept here is choosing an effective, well-tolerated antiemetic with a straightforward dosing option for adult nausea or vomiting. Ondansetron is a 5-HT3 receptor antagonist that blocks nausea signals in both the gut and the brain, making it broadly effective for various causes of nausea, including postoperative and chemotherapy-induced cases. The standard dose is 4 mg, given either IV for rapid relief or orally, which fits many clinical situations. Compared with dopamine antagonists like metoclopramide or prochlorperazine, ondansetron has fewer movement-related side effects, and while diphenhydramine can help, it’s less potent and more sedating for routine use. Therefore, 4 mg of ondansetron by IV or oral route is the typical, best-supported choice for treating nausea or vomiting in adults.