The FDA has announced that the single 32-mg IV dose of ondansetron (Zofran, and generics) used for prevention of cancer chemotherapy-associated nausea and vomiting has been withdrawn from the market because it can prolong the QT interval and could possibly cause a torsades de pointes cardiac arrhythmia. For this indication, the only recommended dose of IV ondansetron is 0.15 mg/kg (maximum 16 mg/dose) every 4 hours for 3 doses. There are no changes in the recommended dosing regimens for oral ondansetron or for IV ondansetron used for prevention of postoperative nausea and vomiting.