FDA: Zofran May Lead to Abnormal Heart Rhythm

The FDA is alerting clinicians that a single 32-mg intravenous dose of ondansetron (Zofran and generics) may lead to QT interval prolongation, which in turn may put patients at risk for torsades de pointes.

In response, the manufacturer is removing the 32-mg dose from the drug's label. The drug, a 5-HT3 receptor antagonist that prevents nausea and vomiting associated with chemotherapy, may still be used at the lower intravenous dose — 0.15 mg/kg given every 4 hours for three doses. No dose should exceed 16 mg.

The following patients may be at particularly high risk for QT prolongation: those with congenital long QT syndrome, congestive heart failure, bradyarrhythmias, or those taking concomitant medications that prolong the QT interval. Before ondansetron is administered, electrolyte abnormalities, such as hypokalemia or hypomagnesemia, should be corrected.

Dosing for oral ondansetron remains the same.