Ru 486 Misconceptions Myths and Morals - ressourcesfeministes

RU 486be the best antiprogesterone developed to date, which isdiscussed in the final section of this chapter.Prostaglandin/Antiprogesterone-induced AbortionIt was in fact Csapo, not Baulieu, as we are often led tobelieve, who first proposed the theory that blockingprogesterone would terminate pregnancy (see also ChapterThree). He recognized that progesterone was vital tomaintain the viability of an embryo implanted in the uterus(Csapo et al., 1973). Pharmaceutical companies subsequentlyresponded to this concept with research and developmentprograms that identified at least four agents withantiprogesterone activity, epostane, RU 486 and two ZKanalogues. Each has been proven to interrupt pregnancy inanimal species such as rats, guinea pigs, sub-human primatesand humans.Experiments have identified unique chemical differencesbetween these antiprogesterones, which account for varyingactivities in different animal species, and the pregnancy-stageat which their action is effective. Elger et al. (1987) comparedthe anti-fertility activity of RU 486 and the ZK analogues,98.299 (onapristone) and 98.734 in the guinea pig 5 todemonstrate differences in their respective activities. Thethree drugs induced abortion in advanced pregnancy, butRU 486, even at the very high dose of 30.0 mg/dayadministered subcutaneously, failed to induce expulsions inmore than 50 per cent of animals. In contrast, ZK 98.734showed dose-dependent effects, was faster acting than RU486, and at a dosage of 30.0 mg/day induced abortion in 100per cent of animals. A quantitative assessment of myometrialPG sensitivity established the optimum duration of RU 486or ZK-priming, with onapristone having significantly greatereffectiveness than ZK 98.734 and RU 486 in elevating themyometrial sensitivity to subsequent administration ofsulprostone or oxytocin.In contrast to Baulieu who posited that RU 486 stimulated106