The effect of fluconazole on the steady-state pharmacokinetics and electrocardiographic pharmacodynamics of terfenadine in humans

Clin Pharmacol Ther. 1993 Jun;53(6):630-6. doi: 10.1038/clpt.1993.83.


Terfenadine is rapidly and nearly completely biotransformed during a first pass to an active acid metabolite. Accumulation of unmetabolized terfenadine has been associated with altered cardiac repolarization. Drug-drug interactions resulting in the accumulation of terfenadine have been reported for ketoconazole and erythromycin. Six subjects were given the recommended dose of terfenadine (60 mg every 12 hours) for 7 days before initiation of oral fluconazole (200 mg once daily). The mean metabolite area under the concentration-time curve increased by 34% and the time to maximum concentration of the metabolite was delayed from 2.3 to 4 hours by concurrent fluconazole. Unmetabolized terfenadine was not present in any subject, and cardiac repolarization was not significantly changed from baseline during any phase of the study. We conclude that a pharmacokinetic interaction between terfenadine and fluconazole exists; however, the absence of accumulation of parent terfenadine in plasma suggests that a clinically significant interaction is unlikely.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Aged
  • Drug Interactions
  • Electrocardiography / drug effects
  • Female
  • Fluconazole / pharmacology*
  • Humans
  • Male
  • Middle Aged
  • Prospective Studies
  • Terfenadine / administration & dosage
  • Terfenadine / blood
  • Terfenadine / pharmacokinetics*


  • Terfenadine
  • Fluconazole