Background: The conventional timing of misoprostol administration after mifepristone for second trimester medical abortion is 36-48 h, but simultaneous administration, which may make the regimen more convenient, has not been studied. The objective of this randomized comparison study is to compare two intervals of administration of misoprostol after pretreatment with mifepristone for second trimester medical abortion.
Methods: Eligible women with gestational age between 12 and 20 weeks were randomized to receive mifepristone 200 mg orally followed by 600 microg misoprostol vaginally either immediately or 36-38 h later, followed by 400 microg vaginal misoprostol every 3 h for a maximum of four doses. The primary outcome measure was the success rate at 24 h after the start of misoprostol treatment and the secondary outcome measures were the induction-to-abortion interval and the frequency of side effects.
Results: There was a significant difference in the success rate at 24 h (36-38 h: 100%; immediate: 91.5%). The median induction-to-abortion interval was significantly shorter in the 36-38 h regimen (4.9 h) compared with the immediate regimen (10 h). Side effects in terms of febrile episodes and chills/rigors were significantly higher in the immediate administration group.
Conclusions: Simultaneous use of mifepristone and misoprostol for second trimester medical abortion is not as effective as the regimen using a 36-38 h dosing interval.