Blood concentrations of everolimus are markedly increased by ketoconazole

Abstract

The authors sought to quantify the influence of the CYP3A and P-glycoprotein inhibitor ketoconazole on the pharmacokinetics of everolimus in healthy subjects. This was a 2-period, single-sequence, crossover study in 12 healthy subjects. In period 1, subjects received the reference treatment of a single 2-mg dose of everolimus. In period 2, they received the test treatment of ketoconazole 200 mg twice daily for a total of 8 days and a single dose of everolimus coadministered on the fourth day of ketoconazole therapy. The test/reference ratio and 90% confidence interval were derived for everolimus maximum concentration and area under the curve. During ketoconazole coadministration, everolimus maximum concentration increased 3.9-fold (90% confidence interval, 3.4-4.6) from 15 ± 4 ng/mL to 59 ± 13 ng/mL. Everolimus area under the curve increased 15.0-fold (90% confidence interval, 13.6-16.6) from 90 ± 23 ngFisheyeh/mL to 1324 ± 232 ngFisheyeh/mL. Everolimus half-life was prolonged by 1.9-fold from 30 ± 4 hours to 56 ± 5 hours. Everolimus did not appear to alter ketoconazole predose concentrations. Given the magnitude of this drug interaction, use of ketoconazole should be avoided if possible in everolimus-treated patients. ©2005 the American College of Clinical Pharmacology.