Pretreatment with mifepristone (RU 486) reduces interval between prostaglandin administration and expulsion in second trimester abortion.

The effect of pretreatment with mifepristone on prostaglandin-induced abortion was investigated in a double-blind randomized trial involving 100 women in the second trimester of pregnancy. The women were randomly allocated to receive either 600 mg oral mifepristone or placebo tablets 36 h before the administration of gemeprost pessaries. The median interval between administration of prostaglandin and abortion was significantly shorter in the mifepristone group (6.8 h) compared with the placebo group (15.8 h). The women pretreated with mifepristone required significantly fewer gemeprost pessaries to induce abortion and experienced significantly less pain than the women who had received placebo.