Metoclopramide (Reglan) can be used to treat vomiting from gastroenteritis, but it is less effective and less well tolerated than ondansetron, which is the preferred option. It works by blocking dopamine receptors and increasing stomach motility, but studies show only modest benefit compared to placebo and clear inferiority to ondansetron in stopping vomiting and speeding recovery. Side effects such as drowsiness, tremor, and movement-related problems are more common, so it should be used cautiously, mainly in adults when ondansetron is not available or cannot be given. It is generally not recommended for children due to limited benefit and safety concerns.