US FDA warns of heart rhythm problems with GSK's anti-nausea drug Zofran

The US Food and Drug Administration has notified health care professionals and patients of an ongoing safety review and labeling changes for the anti-nausea drug Zofran (ondansetron, ondansetron hydrochloride and generics).

The drug was originated by UK pharma giant GlaxoSmithKline (LSE: GSK), and markets it as Zofran, which is now exposed to generic competitors. Prior to the advent of copy versions, the drug generated annual sales in the region of $840 million.

The agency says that ondansetron may increase the risk of developing prolongation of the QT interval of the electrocardiogram, which can lead to an abnormal and potentially fatal heart rhythm, including Torsade de Pointes. Patients at particular risk for developing Torsade de Pointes include those with underlying heart conditions, such as congenital long QT syndrome, those who are predisposed to low levels of potassium and magnesium in the blood, and those taking other medications that lead to QT prolongation.