What is a common IV dose for ondansetron used in the ED?

• A. 4 mg IV
• B. 8 mg IV
• C. 2 mg IV
• D. 6 mg IV

Answer: (A)

Ondansetron works by blocking 5-HT3 receptors in both the gut and central nervous system, which stops the signals that trigger nausea. When used in the ED, a single fixed IV dose is common because it delivers rapid relief with a straightforward administration and consistent effect across many adults. The goal is quick control of symptoms with the smallest amount needed to minimize side effects, since higher or repeated doses can increase the risk of QT interval prolongation and other adverse effects. If persistent nausea occurs, a second dose may be considered after a few hours, but with attention to heart rhythm and potential drug interactions. Pediatric dosing is usually weight-based, reflecting different pharmacodynamics in children.