FDA: Single IV dose of ondansetron may cause potentially fatal heart rhythms

FDA is alerting healthcare professionals to the possibility that a 32-mg single intravenous dose of ondansetron (Zofran, ondansetron hydrochloride, and generics) could lead to QT interval prolongation, putting patients at risk for a potentially fatal heart rhythm known as Torsades de Pointes.

Ondansetron, a 5-HT3 receptor antagonist, is used to prevent nausea and vomiting associated with cancer chemotherapy, radiation therapy, and surgery.

The safety announcement follows the release of preliminary results from a recently completed manufacturer-conducted clinical study. As part of the ongoing safety review of ondansetron, GlaxoSmithKline (GSK) was required by FDA to assess the potential for the drug to prolong the QT interval.

The 32-mg single intravenous dose will be removed from the Zofran drug label, which will state that no single intravenous dose should exceed 16 mg. The updated label will state that ondansetron can continue to be used in adults and children with chemotherapy-induced nausea and vomiting at the lower intravenous dose recommended in the drug label, a dose of 0.15 mg/kg administered every 4 hours for 3 doses. 

FDA says it will evaluate the final study results when complete, and will continue to work with GSK to explore a safe alternative single dose regimen. Meanwhile, the agency notes that adverse events should be reported to the FDA MedWatch program.