A Case of Torsade de Pointes after Combined Use of Terfenadine and Itraconazole

ABSTRACT

Torsade de pointes is a life-threatening, polymorphic ventricular tachycardia associated with prolongation of the QTc interval. Although torsade de pointes is found in many clinical settings, it is mostly drug induced. Similar problems have been described with nonsedating H1-selective antihistamines like terfenadine and astemizole. The increased risks of both H1-antihistamines were associated with exposure to supratherapeutic doses or concomitant exposure to the cytochrome P-450 inhibitors, ketoconazole, erythromycin and cimetidine. We report a 51-year-old woman with torsade de pointes and a long QTc interval caused by the combined use of terfenadine and itraconazole. After discontinuation of these drugs and treatments with electrical cardioversion and magnesium sulfate, torsade de pointes and prolonged QTc interval were no longer observed and she was discharged in good condition with a normal ECG. In conclusion, physicians should be aware that terfenadine and astemizole can cause torsade de pointes in rare cases.