Can oral contraceptive steroids influence the elimination of nifedipine and its primary pryidine metabolite in humans?

Objective: To investigate the influence of oral contraceptives on cytochrome P450 3A4 (P450NF) activity.

Methods: In 23 healthy women, the pharmacokinetics of nifedipine and its main metabolite dehydronifedipine in plasma were assessed after a single oral dose, prior to and after intake of one of two oral contraceptive formulations, one containing 2 mg dienogest and 0.03 mg ethinylestradiol (group A) and the other containing 0.