A systematic review cd002855 summarized clinical outcomes and adverse effects of medical abortion regimens consisting of mifepristone followed by buccal misoprostol. 20 studies with a total of 33 846 women through 70 days of gestation were included. The overall efficacy was 96.7% (95% CI 96.5 to 96.8%) and the continuing pregnancy rate was 0.8% (95% CI 0.7 to 0.9%) in approximately 33 000 pregnancies through 63 days of gestation. Only 332 women with pregnancies between 64 and 70 days of gestation were reported with an overall efficacy of 93.1% (95% CI 89.6-95.5%) and a continuing pregnancy rate of 2.9% (95% CI 1.4-5.7%). Regimens with a 24-hour time interval between mifepristone and buccal misoprostol administration were slightly less effective than those with a 24- to 48-hour interval. Rates of surgical evacuation for reasons other than ongoing pregnancy range from 1.8% to 4.2%. Severe adverse events like blood transfusion (0.03-0.6%) and hospitalization (0.04-0.9%) are uncommon.
Another systematic review 2 summarized the effectiveness and safety of regimens using the lower mifepristone dose, 200 mg, followed by misoprostol in early pregnancy. 87 trials with a total of 47 283 women were included. Treatment failure occurred in 2 192 (4.8%) of subjects. Ongoing pregnancy was reported in 1.1% (499/45 150) of the evaluable subjects in the 117 trial groups reporting this outcome. The risk of medical abortion failure was higher among trial groups in which at least 25% of subjects had gestational age over 8 weeks, the specified interval between mifepristone and misoprostol was less than 24 h, the total misoprostol dose was 400 mcg (rather than higher), or the misoprostol was administered by the oral route (rather than by vaginal, buccal, or sublingual routes). Across all trials, 119 evaluable subjects (0.3%) were hospitalized, and 45 (0.1%) received blood transfusions.
A Cochrane review [Abstract] 1 included 99 studies. Mifepristone (MIF, antiprogesterone) alone is less effective compared to the combined regimen mifepristone/prostaglandin (RR 3.76 95% CI 2.30 to 6.15; effectiveness measure = failure to achieve complete abortion). MIF 600 mg compared to 200 mg in the combined regimen shows similar effectiveness (RR 1.07, 95% CI 0.87 to 1.32; 4 trials, n=3484). Misoprostol (MIS, prostaglandin) administered orally is less effective (more failures) than the vaginal route (RR 2.38, 95% CI 1.46 to 3.87; 3 RCTs, n=1704) and may be associated with more frequent side effects such as nausea and diarrhoea. Sublingual and buccal routes were slightly less effective compared to the vaginal route. 19 trials comparing prostaglandin alone to the combined regimen (mifepristone, letrozole, estradiol valerate, tamoxifen, or methotrexate plus prostaglandin) reported higher risk of failure (RR of failure 2.39, 95% CI 1.89 to 3.02; 18 RCTs, n=3471).
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