PPIs do not directly cause prolongation of the QT interval, but they have been associated with hypomagnesemia, which is often accompanied by hypocalcemia and hypokalemia and can result in cardiac repolarization disturbances such as QT interval prolongation.2 Reports have described cases of QT interval prolongation and TdP associated with severe PPI-induced hypomagnesemia.3,4 TdP has also been reported in patients taking a PPI concomitantly with drugs that directly prolong the QT interval.5,6 The newer PPIs dexlansoprazole (Dexilant) and rabeprazole (Aciphex, and generics) have not been linked to QT interval prolongation or TdP to date, but they can cause hypomagnesemia.

Serum magnesium levels should be monitored periodically in patients taking a PPI for an extended period of time (>2 weeks). If possible, extended PPI therapy should be avoided in patients who require treatment with drugs that carry a known risk of TdP7 and in those with long QT syndrome. If extended PPI therapy must be used with a drug that prolongs the QT interval, close monitoring of magnesium levels and the QT interval is recommended.