Response to the antiprogestagen RU 486 (mifepristone) during early pregnancy and the menstrual cycle in women

Abstract

RU 486 has wide potential utility as an abortifacient drug when used within the first 6 weeks of pregnancy and has the ability to induce an abortion in about 80% of subjects. Administration of low doses of prostaglandins together with RU 486 increases the success rate. It is possible that alterations in metabolism of RU 486 may explain non-responsiveness to the drug in some women. Mid-luteal phase administration of RU 486 produces bleeding within 72 h and in one-third of subjects there was luteolysis with decrease in serum FSH, oestradiol and progesterone concentrations. Administration of RU 486 in the late luteal phase does not disturb menstrual cycle length, bleeding patterns, ovulation, or hormonal parameters in treatment or posttreatment cycles. However, the drug alone cannot be used as a 'menses regulator' or 'once monthly pill' since some pregnancies do continue. Possibly the efficacy of RU 486 may be enhanced when it is combined with prostaglandins or other agents. Administration of RU 486 in the follicular phase blocks ovulation, delays the LH surge, and is associated with low concentrations of oestradiol. This is presumably the result of gonadotrophin inhibition.

PIP: RU486 has wide potential utility as an abortifacient agent when used within the 1st 6 weeks of pregnancy. It had the ability to induce an abortion in about 80% of the subjects on which it is used. Administration of low doses of prostaglandins (PGs) together with RU 486 increases the success rate. It is possible that alterations in metabolism of RU 486 may explain nonresponsiveness to the drug in some women. Midluteal phase administration of RU 486 produces bleeding within 72 hours and in 1/3 of subjects, there was luteolysis with decrease in serum FSH, estradiol, and progesterone concentrations. RU 486 administration in the late luteal phase does not disturb the menstrual cycle length, bleeding patterns, ovulation, or hormonal parameters in treatment or posttreatment cycles. However, the drug alone cannot be used as a menses regulator or a once-a-month pill since some pregnancies do continue. Possibly, the effect of RU 486 may be enhanced when it is combined with PGs or other agents. Administration of RU 486 during the follicular phase blocks ovulation, delays LH surges, and is associated with low concentrations of estradiol. This is presumably the result of gonadotropin inhibition.