Which of the following is a standard antiemetic dose for adults?

• A. Zofran: 4 mg IV/IO/PO
• B. Zofran: 8 mg IV
• C. Zofran: 1 mg IV
• D. Zofran: 2 mg IV

Answer: (A)

Ondansetron’s standard single-dose for adults is 4 mg, and it can be given IV, IO, or orally. This amount provides reliable antiemetic effect while staying within a safety window, balancing efficacy with the risk of side effects. Doses smaller than this (such as 1 mg or 2 mg) are typically not considered standard for routine antiemetic use, and a higher dose like 8 mg IV isn’t the typical single-dose choice because it can increase the risk of QT interval prolongation and other adverse effects. If needed, dosing can be repeated within the overall daily limit (up to about 24 mg per day), but the standard single-dose remains 4 mg.