Rapid Occurrence of QT Prolongation and Torsades de Pointes after Combined Administration of Itraconazole and Terfenadine

Torsades de pointes, a potentially life-threatening polymorphic ventricular arrhythmia, can occur with a variety of congerital and acquired conditions. An 80 year-old female who had been receiving itraconazole for 2 months for onycomycosis developed QT prolongation and torsades de pointes 27 hours after the coadministration of terfenadine. The rapid onset of this complication may be due to the combined effects of drug interaction and terfenadine overdose. A detailed history should be taken before prescribing either drug and their combination should be avoided.