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.