recommended dose for ondansetron
1 However, no single intravenous dose of ondansetron should exceed 16 mg due to the risk of QT prolongation. 2  The new information does not change any of the recommended oral dosing regimens for ondansetron, including the single oral dose of 24 mg for chemotherapy induced nausea and vomiting.ECOMMENDATION: The new information on QT prolongation does not change any of the recommended oral dosing regimens for ondansetron. It also does not change the recommended lower dose intravenous dosing of ondansetron to prevent post-operative nausea and vomiting.