Effect of itraconazole on the pharmacokinetics of everolimus administered by different routes in rats

The effect of itraconazole on the pharmacokinetics of everolimus was investigated in rats. Ten minutes after an intravenous or intraintestinal administration of itraconazole, everolimus was delivered intravenously (0.2 mg/kg) or intraintestinally (0.5 mg/kg). Blood concentrations of everolimus were measured up to 240 min, and pharmacokinetic parameters were calculated. Intraintestinally administered itraconazole (20 mg/kg) significantly increased the area under the concentration-time curve (AUC) of intraintestinally administered everolimus about 4.5-fold, but even at 50 mg/kg did not affect the AUC of intravenously administered everolimus. However, intravenously administered itraconazole (50 mg/kg) increased the AUC of both intraintestinally and intravenously administered everolimus approximately 2-fold. Using a value for hepatic blood flow from the literature (50 ml/min/kg), the apparent intestinal and hepatic extraction of everolimus without itraconazole was calculated as about 80% and 13%, respectively. Intraintestinally administered itraconazole (20 mg/kg) changed the apparent intestinal extraction by 0.26-fold from 0.829 to 0.215, but the hepatic availability of everolimus was almost unchanged after the intravenous or intraintestinal administration of itraconazole even at a dose of 50 mg/kg from 0.871 to 0.923 or 0.867, respectively. In conclusion, intraintestinally administered itraconazole dramatically increased the AUC of everolimus delivered intraintestinally by inhibiting the intestinal first-pass extraction of this drug.