Vaginal progesterone for contraception.

Silastic vaginal rings impregnated with progesterone (P) or progesterone and estradiol (E) were used in nine women for thirty 21-day cycles to study the effect on ovarian function. The average daily rates of release of P and E from the rings were 2.2 mg/day and 220 microgram/day, respectively. In anovulatory treatment cycles the mean plasma level of P was 0.9 ng/ml. E levels fluctuated in the range seen in normally cycling women due to endogenous E production. In a menopausal woman the E levels increased to 50 to 100 pg/ml during treatment and FSH levels declined. Ovulation occurred in 18 (60%) of the treated cycles, and resulted in one pregnancy. Although the results rule out the use of these rings for contraceptive purposes, they indicate that at higher dosages the Silastic vaginal ring offers a mode of administration of natural steroids to be used in hormonal contraception.