The minimum serum levels of levonorgestrel at steady state are 1.9 ± 1 ng/mL. At steady state, attained from day 19 onwards, maximum levonorgestrel concentrations of 6 ± 2.7 ng/mL are reached at 1.5 ± 0.5 hours after the daily dose. Ethinyl estradiol is rapidly and almost completely absorbed from the gastrointestinal tract but, due to first-pass metabolism in gut mucosa and liver, the bioavailability of ethinyl estradiol is between 38% and 48%.Īfter a single dose of levonorgestrel and ethinyl estradiol to 22 women under fasting conditions, maximum serum concentrations of levonorgestrel are 2.8 ± 0.9 ng/mL (mean ± SD) at 1.6 ± 0.9 hours. However, literature indicates that levonorgestrel is rapidly and completely absorbed after oral administration (bioavailability about 100%) and is not subject to first-pass metabolism. No specific investigation of the absolute bioavailability of levonorgestrel and ethinyl estradiol in humans has been conducted.
Although the primary mechanism of this action is inhibition of ovulation, other alterations include changes in the cervical mucus (which increase the difficulty of sperm entry into the uterus) and the endometrium (which reduce the likelihood of implantation). Larissia - Clinical Pharmacology Mode of ActionĬombination oral contraceptives act by suppression of gonadotropins.
