Steady-state pharmacokinetics of an extended-regimen oral contraceptive with continuous estrogen.

Background: This study was conducted to evaluate the steady-state blood concentrations and potential accumulation of levonorgestrel (LNG) and ethinyl estradiol (EE) administered for up to 84 days and EE alone for 7 additional days as an extended-regimen 91-day oral contraceptive (OC).

Study Design: An open-label, single-site study was conducted in 30 healthy female volunteers. Subjects received daily doses of 0.15 mg LNG/0.03 mg EE for 84 consecutive days followed by 0.03 mg EE alone for 7 days. Pharmacokinetic (PK) monitoring was conducted on Days 1, 21, 84 and 91.

Results: The observed plasma concentrations of LNG after 84 days and of EE after 84 and 91 days were comparable to the steady-state concentrations observed at 21 days. Pharmacokinetic parameters over the 24-h dosing period were similar at all time points measured after achieving steady-state plasma concentrations.

Conclusion: This study demonstrated that an extended-regimen OC providing 84 days of LNG/EE and 7 days of EE alone has a PK profile similar to a 28-day conventional OC regimen and does not result in any additional accumulation of these hormones.