The FDA is informing healthcare professionals that preliminary results from a recently completed clinical study suggest that a 32mg single intravenous dose of ondansetron (Zofran; GlaxoSmithKline and generics) may affect the electrical activity of the heart (QT interval prolongation), which could pre-dispose patients to develop an abnormal and potentially fatal heart rhythm known as Torsades de Pointes.

The Zofran drug label will be changed to remove the 32mg single intravenous dose. It will also 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 0.15mg/kg administered every 4 hours for three doses; however, no single intravenous dose should exceed 16mg. Healthcare professionals are recommended to correct any electrolyte abnormalities (eg, hypokalemia or hypomagnesemia) prior to the infusion of ondansetron.

Ondansetron is a selective 5-HT3 receptor antagonist indicated for prevention of nausea and vomiting associated with initial and repeat courses of emetogenic cancer chemotherapy, including high-dose cisplatin, and prevention of post-op nausea and vomiting.

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