Final answer:
The contraindications for ondansetron include hypersensitivity to the drug, a history of QT prolongation, and co-administration with drugs that prolong the QT interval.
Step-by-step explanation:
The contraindications for ondansetron under the Nausea/Vomiting Medical Directive include hypersensitivity to the drug, a history of QT prolongation or other risk factors for QT prolongation, and co-administration with drugs that are known to prolong the QT interval.
For example, ondansetron should not be used in patients with a known hypersensitivity to the drug, as it can cause allergic reactions.
Additionally, ondansetron should not be used in patients with a history of QT prolongation, as it can further prolong the QT interval and potentially lead to dangerous cardiac arrhythmias.