Effects of single and multiple doses of itraconazole on the pharmacokinetics of fexofenadine, a substrate of P-glycoprotein.
OBJECTIVE
We determined whether or not the extent of drug interaction of fexofenadine by itraconazole is time-dependent.


METHODS
In a randomized two-phase crossover study, itraconazole was administered orally for 6 days, and, on days 1, 3 and 6, fexofenadine was administered simultaneously. On another occasion, fexofenadine was administered alone.


RESULTS
Itraconazole increased fexofenadine AUC(0, infinity), and the % change for difference was 178% (95% CI 1235, 3379), 205% (95% CI 1539, 3319) and 169% (95% CI 1128, 2987) on days 1, 3 and 6 of the 6 day treatment, respectively.


CONCLUSIONS
The extent of drug interaction by itraconazole was not time-dependent.
Shimizu
Mikiko
M
Department of Clinical Pharmacology, Hirosaki University School of Medicine, Hirosaki, Japan.
Uno
Tsukasa
T
Sugawara
Kazunobu
K
Tateishi
Tomonori
T
D000328:Adult; D000935:Antifungal Agents / Q000008:administration & dosage* / Q000494:pharmacology; D018592:Cross-Over Studies; D004347:Drug Interactions; D005260:Female; D039563:Histamine H1 Antagonists, Non-Sedating / Q000493:pharmacokinetics*; D006801:Humans; D017964:Itraconazole / Q000008:administration & dosage* / Q000494:pharmacology; D007564:Japan; D008297:Male; D016593:Terfenadine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics
D000935:Antifungal Agents; D039563:Histamine H1 Antagonists, Non-Sedating; D017964:Itraconazole; D016593:Terfenadine; C093230:fexofenadine