[A new cause of torsades de pointes: combination of terfenadine and troleandomycin].

The authors report a case of wave-burst arrhythmia which occurred during combined treatment with terfenadine and troleandomycin. After the treatment had been stopped and the QT interval returned to normal, terfenadine treatment was reintroduced with no major change in repolarization. However, as soon as troleandomycin was associated, there was a significant and progressive prolongation of QT. Normal repolarization was restored again with troleandomycin alone. These findings suggest drug interaction between terfenadine and troleandomycin. Although it is not possible to carry out serum assays of terfenadine, one possible physiopathological hypothesis would be an overdose of terfenadine. Terfenadine undergoes hepatic oxidative metabolism involving the cytochrome P450 pathway and troleandomycin inhibits cytochrome P450. In the literature, a case has already been described of wave-burst arrhythmia related to terfenadine overdose when associated with a cytochrome P450 inhibitor.