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Nearly three years ago, the FDA warned U.S. physicians about the potential adverse cardiac effects of combining terfenadine with either ketoconazole or erythromycin. Despite this attention, deaths from cardiac arrhythmias in patients taking terfenadine continue to be reported. Two studies in a recent issue of JAMA address this important issue.
One study reviewed cases of torsades de pointes, the severe ventricular arrhythmia associated with terfenadine intake, reported to the FDA. Of the 25 reported cases, two patients died and the others required hospitalization. The researchers found that it is the parent drug terfenadine, not its major metabolite, that blocks potassium channels, causing substantial prolongation of the QT interval. A prolo…