Pharmacodynamic effects of ethinyl estradiol in women using vaginal devices releasing small doses of levonorgestrel at a constant rate.

Eight normally menstruating women were provided with vaginal devices releasing levonorgestrel (NOG)4) at a constant rate of 20 micrograms/24 h. On day 71 or 72 following the insertion of the device, oral doses of 50 micrograms of ethinyl estradiol (EE) were administered daily for one week. Peripheral blood samples were drawn three times weekly during a pretreatment (control) cycle and from day 29 of the treatment period. The levels of progesterone (P), estradiol (E2) and NOG were measured by radioimmunoassay, sex hormone binding globulin (SHBG) by a steady state polyacrylamide gel electrophoresis and the percentage of binding of NOG, testosterone (T) and E2 by equilibrium dialysis of diluted plasma. An endometrial smear and a biopsy were taken from each subject on 3 occasions, viz. during the control cycle (cycle day 20-22), during the period with the NOG-releasing device in situ (44-50 days after the insertion of the device), and on the 7th day of concomitant EE administration.