IV rehydration is a powerful marker of treatment failure and reducing the need for IV rehydration therapy in either of these 2 groups of children will be viewed as a significant advance by healthcare providers and decision makers. Previous studies of ondansetron have not been conducted in low and middle income countries (LMIC), have been of relatively small sample sizes, have not employed WHO dehydration scales, and have not focused on young children (i.e. <5 years). As such therapy is unavailable to a large number of children in LMIC countries, the ability to demonstrate that ondansetron can reduce the use of IV rehydration will provide compelling evidence that this drug has the potential to save lives around the world. We postulate that oral ondansetron administration to children in LMIC, if beneficial in our study population, could serve as a feasible and reliable intervention that is available for provision by non-hospital based, outreach, and healthcare providers in remote regions of the world.