The nausea drug ondansetron (Zofran) may cause QT prolongation after a single 32-mg intravenous dose, the FDA warned.

Patients could therefore be at risk for torsades de pointes, a life-threatening arrhythmia, the agency said, adding that the drug's manufacturer is removing the single 32-mg dose from its label.

Ondansetron is indicated for chemotherapy-induced nausea and vomiting and, at lower doses, for postoperative nausea and vomiting.

The FDA had previously indicated that it was  http://www.medpagetoday.com/HematologyOncology/Chemotherapy/28538 - investigating the arrhythmogenic potential of ondansetron  in collaboration with the drug's maker, GlaxoSmithKline.

Preliminary results of a study ordered by the FDA found a maximum mean difference in QTcF of 20 msec after the 32-mg IV dose.

An IV dose of 8 mg, on the other hand, led to a mean maximum QTcF difference of 6 msec.

The drug's new label will indicate that ondansetron can be used in adults and children at doses of 0.15 mg/kg every 4 hours for up to three doses, but no single dose should exceed 16 mg.

No changes are contemplated at this point for instructions on oral dosing. Currently, oral doses of up to 24 mg are approved.

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