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  • Title: Sequential regimen of the antiprogesterone RU486 and synthetic progestin for contraception.
    Author: Kekkonen R, Lähteenmäki P, Luukkainen T, Tuominen J.
    Journal: Fertil Steril; 1993 Oct; 60(4):610-5. PubMed ID: 8405512.
    Abstract:
    OBJECTIVE: To examine the effect of sequential use of the antiprogesterone RU486 and synthetic progestin on ovarian function of healthy women. DESIGN: Healthy women were given a sequential antiprogesterone-progestin treatment. Blood samples were taken twice a week during one control cycle and one to three treatment cycles; prospective analysis. SETTING: The outpatient clinic of the Helsinki City Maternity Hospital, Helsinki, Finland, and Steroid Research Laboratory, Department of Medical Chemistry, University of Helsinki, Helsinki, Finland. PATIENTS: Eleven healthy women, volunteers, 20 to 34 years of age. INTERVENTIONS: A dose of 25 mg/d of RU486 was given during cycle days 1 to 21, and synthetic progestin (5 mg of norethisterone to six and 5 mg of medroxyprogesterone acetate to five women) during cycle days 22 to 31. MAIN OUTCOME MEASURES: Serum P, E2, FSH, and LH were measured from serum samples. RESULTS: In 20 of the 24 treatment cycles analyzed the serum concentrations of P were anovulatory. In the remaining 4 cycles, P levels rose above 3 ng/mL, suggestive of ovulation. Folliculogenesis was not completely inhibited, but serum E2 profiles were subnormal and delayed. Bleeding control was satisfactory. CONCLUSIONS: Antiprogesterone RU486 hampers or delays follicular development, suggesting a possible use as an estrogen-free oral contraceptive. However, the synthetic progestins used in this regimen induced serum P rises in some cycles. The synthetic progestin provides the cycle control, but its possible effect on the reliability of the method remains to be evaluated. To assess the effectiveness of an estrogen-free oral contraceptive (OC) involving the sequential administration of an antiprogesterone and synthetic progestin, 11 healthy Finnish women 20-34 years of age were enrolled in a prospective investigation for 1-3 cycles. 25 mg of RU-486 was administered for the first 21 days of the cycle, followed by 5 mg of norethisterone or medroxyprogesterone acetate for the next 10 days. It was hypothesized that prolonged RU-486 administration would prevent the follicle from surviving for ovulation. During the RU-486 phase, P increases above 3 ng/ml (suggestive of ovulation) were recorded in only four of the 24 treatment cycles analyzed. Mean serum estradiol concentrations were 147 pg/ml in ovulatory women and 72 pg/ml in anovulatory women, indicating that follicle development was subnormal and delayed, but not completely inhibited. Baseline secretion of luteinizing hormone (LH) increased during RU-486 administration, while an LH surge greater than 100% over baseline was recorded in the majority of cycles during progestin administration. No significant changes occurred in follicle-stimulating hormone levels. Menstrual bleeding began 1-5 days after progestin discontinuation; women who took norethisterone experienced no breakthrough bleeding or spotting during treatment. It is concluded that the main antiovulatory effect of RU-486 is attributable to its antiprogestational effect on the preovulatory P rise.
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