Torsades de pointes occurring in association with terfenadine use

JAMA. 1990 Dec 5;264(21):2788-90.


Torsades de pointes is a form of polymorphic ventricular tachycardia that is associated with prolongation of the QT interval. Although found in many clinical settings, torsades de pointes is most often drug induced. This report describes the first association (exclusive of drug overdose) of symptomatic torsades de pointes occurring with the use of terfenadine in a patient who was taking the recommended prescribed dose of this drug in addition to cefaclor, ketoconazole, and medroxyprogesterone. Measured serum concentrations of terfenadine and its main metabolite showed excessive levels of parent terfenadine and proportionately reduced concentrations of metabolite, suggesting inhibition of terfenadine metabolism. We believe that a drug interaction between terfenadine and ketoconazole resulted in the elevated terfenadine levels in plasma and in the cardiotoxicity previously seen only in cases of terfenadine overdose.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Benzhydryl Compounds / adverse effects*
  • Drug Interactions
  • Female
  • Histamine H1 Antagonists / adverse effects*
  • Humans
  • Ketoconazole / adverse effects
  • Terfenadine
  • Torsades de Pointes / chemically induced*
  • Torsades de Pointes / physiopathology


  • Benzhydryl Compounds
  • Histamine H1 Antagonists
  • Terfenadine
  • Ketoconazole