Torsades de pointes induced by the concomitant use of ivabradine and azithromycin: an unexpected dangerous interaction.

A 68-year-old man had a cardiac syncope. He was known to have a long QT-interval and was treated with ivabradine for paroxysmal sinusal tachycardia. In the last 5 days, azithromycin had been prescribed for sinusitis. An electrocardiogram showed torsades de pointes (TdP). Azithromycin is known to prolong the QT-interval. Ivabradine does not affect the QT-interval but has a conditional risk of TdP when taken with other drugs that block its metabolic breakdown. This case presents the specific problem of a patient with long QT who received two medications, which may interact and prolong the QT.