Mifepristone (RU486), an analogue of the progestin norethindrone, has strong affinity for the progesterone receptor but acts as an antagonist, blocking the effect of natural progesterone. Given alone, the drug was moderately effective in causing abortion of early pregnancy; the combination of mifepristone with a low dose of prostaglandin proved very effective, producing complete abortion in 96% to 99% of cases (330). The FDA approved a protocol of mifepristone, 600 mg orally, followed 2 days later by misoprostol, 400 mg, taken orally in women no more than 49 days from start of the last menstrual period. In the years before FDA approval, investigators established the superiority of the evidence-based protocols that are used. These protocols used 200 mg of mifepristone rather than 600 mg, because the lower dose is just as effective. Misoprostol, 800 μg is given by vaginal or buccal routes, which provides higher efficacy than the 400 μg oral dose (331–334). The misoprostol can be taken at 24, 48, or 72 hours after mifepristone with equal efficacy (333). Women may safely self-administer the misoprostol at home (334). It can be taken by buccal or vaginal routes with similar blood levels and similar areas under the plasma concentration curve (AUC) (335,336). After case reports of death from Clostridium sordelli, a large cohort study was published by Planned Parenthood describing use of prophylactic doxycycline 100 mg twice a day for one week, and buccal rather than vaginal administration of misoprostol (337).
Contraindications to medical abortion with mifepristone/misoprostol include ectopic pregnancy; an IUD in place (remove IUD first); chronic adrenal failure; concurrent longterm corticosteroid therapy; history of allergy to mifepristone, misoprostol, or other prostaglandin; and the inherited porphyrias (338). The mifepristone–misoprostol combination was studied for gestations at 9 to 13 weeks; although it is almost as effective as earlier in pregnancy, a larger proportion of patients will experience heavy bleeding and require vacuum curettage (339).
Alternatives to medical abortion when mifepristone is not available include regimens with methotrexate/misoprostol and misoprostol alone. The antifolate methotrexate provides another medical approach to pregnancy termination, but takes longer than the technique using mifepristone/misoprostol (340). Medical abortion can be induced with misoprostol alone, although it is less effective than the mifepristone/misoprostol combination. Vaginal misoprostol, 800 μg, repeated in 24 hours if fetal expulsion has not occurred, produces a complete abortion in 91% of pregnancies up to 56 days of amenorrhea (341).
Complications of Medical Abortion