Uses of RU 486: a clinical update.

: RU 486, a steroid with antiprogesterone and antiglucocorticoid properties, is currently in phase II clinical trials. To date, over 1000 women have been treated with RU 486 for various purposes. In pregnancies of less than 5 weeks' amenorrhea, 600 mg of RU 486 has led to interruption of pregnancy with complete expulsion of the uterine content in approximately 90% of cases, without any need for additional surgical procedures. The success rate declines with increasing duration of pregnancy: complete interruption and expulsion has been recorded in only 58% of pregnancies over 6 weeks' duration. An average of 2.5 days elapses between RU 486 intake and the onset of uterine bleeding. Trials are in progress to determine if the addition of oxytocic agents such as prostaglandins will decrease the rate of incomplete abortion in more advanced pregnancies, reduce the amount of uterine bleeding, and speed up the occurrence of complete abortion. RU 486 has further been noted to result in cervical ripening, and trials are underway to identify optimal conditions for using RU 486 to prepare the cervix for vacuum aspiration or dilatation and curettage. In addition, large scale studies are in progress to assess the preliminary observation that RU 486 leads to complete fetal expulsion within 72 hours in the case of 2nd-trimester fetal death in utero. No major side effects have been associated with RU 486, even when administered in large doses. Finally, data obtained in nonpregnant women indicate that, when given in the mid-luteal phase in large amounts, RU 486 may exert luteolytic effects in addition to its endometrial action. Studies are underway to determine if these findings can be extrapolated to women in whom fertilization has occurred.