The in vitro metabolism of ethinyloestradiol, mestranol and levonorgestrel by human jejunal mucosa.

ABSTRACT

PIP: In vitro studies were conducted on the metabolism of 3 steroids used in OCs (oral contraceptives) by small pieces of human jejunal mucosa. This was done because the gastrointestinal mucosa of humans is known to metabolise a number of drugs. Almost 40% of the ethinyl estradiol, 9.8% of the levonorgestrel, and 7% of the mestranol were metabolised after incubation. All these metabolic responses were significantly different from those in the control groups. Results of the study show that the metabolism of the ethinyl estradiol was related to the weight of the tissue used. These results are consistent with the known marked 1st pass effect of ethinyl estradiol. Norgestrel, known to have little or no 1st pass effect, did not show a high rate of gut metabolism. Under the experimental conditions employed, no Phase 1 metabolism of either ethinyl estradiol or levonorgestrel was apparent.