Late luteal phase administration of RU486 for three successive cycles does not disrupt bleeding patterns or ovulation

Abstract

RU486, a 19-nor steroid, binds with high affinity to the receptors for progesterone and glucocorticoids, blocking the actions of these hormones on their target tissues. We conducted studies to determine whether RU486 administered at the end of the luteal phase would disturb the menstrual rhythm, ovulation, or hormonal parameters in the treatment and posttreatment cycles. The first study was done in six surgically sterilized women during two consecutive cycles. RU486 [17βQ-hydroxy-11β-(4-dimethylaminophenyl)17α-(1-propynyl)estra-4, 9-dien-3-one; 100 mg/day] was given for 4 consecutive days, commencing on days 23-27 of the first cycle. Menstrual bleeding occurred by the second day of RU486 administration in all women and was indistinguishable from their usual bleeding pattern. The onset of this bleeding was advanced by RU486 administration, since it entailed shortening of the luteal phase with prolongation of the following follicular phase. Serum LH, FSH, estradiol, and progesterone leve