Termination of early human pregnancy with either 50 mg or 200 mg single oral dose of mifepristone (RU486) in combination with either 0.5 mg or 1.0 mg vaginal gemeprost

Abstract

Mifepristone (RU486) is licensed for use in France at a dose of 600 mg in combination with 1.0 mg of vaginal gemeprost (a prostaglandin E1 analogue) for medical termination of early pregnancy up to 7 weeks' amenorrhoea resulting in 96% complete abortion rates. This study examines if it is possible to use lower doses of mifepristone and gemeprost to achieve similar success for women with pregnancies up to 56 days' amenorrhoea. Four groups of 25 women were scheduled to be given single oral doses of either 50 mg or 200 mg of mifepristone followed 48 hours later by insertion of a single vaginal pessary of 0.5 mg or 1.0 mg gemeprost. The lowest dose combination (i.e. 50 mg mifepristone + 0.5 mg gemeprost) was found to have unacceptable efficacy with a complete abortion rate of only 82%; the highest dose combination (i.e. 200 mg mifepristone + 1.0 mg gemeprost) resulted in a satisfactory complete abortion rate of 96% which is comparable with the rates for the recommended high 600 mg mifepristone dose (+ 1.0 mg gemeprost) in routine clinical use in France. The current study shows that efficacy can be maintained using a third of the recommended dose of mifepristone.