Relative bioavailability of ethinyl estradiol from two different oral contraceptive formulations after single oral administration to 18 women in an intraindividual cross-over design.

Two low-dose oral contraceptives, both containing the same dose of ethinyl estradiol (EE2) but different progestins (gestodene and desogestrel, respectively), were compared with respect to the relative bioavailability of EE2. After single-dose administration of both formulations to 18 women in an intraindividual cross-over design, there was no difference in the target variables for EE2 (Cmax, tmax and AUC). With respect to EE2, both formulations were bioequivalent. The observation of others, reporting higher EE2 levels in the serum of women taking the gestodene-containing formulation as compared to those taking the desogestrel-containing formulation, was not confirmed.