5-hydroxytryptamine (5HT3) receptor antagonists are a class of antiemetic drug used to relieve nausea and vomiting associated with chemotherapy. At this time, four 5HT3 receptor antagonists are approved by the U.S. Food and Drug Administration, ondansetron, granisetron, dolasetron, and palonosetron. There is limited evidence that palonosetron may have a greater efficacy in the prevention of delayed chemotherapy-induced nausea and vomiting. Ramosetron also is a type of 5HT3. 5HT3 receptor antagonists are effective in both adult and pediatric patients. However, among pediatric patients, appropriate use and dosing for various age groups have not been established.