A comparison of isosorbide mononitrate, misoprostol and combination therapy for first trimester pre-operative cervical ripening: a randomised controlled trial

Abstract

Objective To determine whether a combined therapy with isosorbide mononitrate (40mg) and misoprostol (400μg) for pre-operative cervical ripening in the first trimester would result in improved clinical effectiveness, and fewer side effects compared with each agent used alone. Design Randomised controlled trial. Setting Glasgow Royal Infirmary. Population Sixty-six primigravid women scheduled for suction termination of pregnancy. Methods Women were randomly assigned to receive before surgery, per vaginam, isosorbide mononitrate 40 mg ( n=22), misoprostol 400 μg ( n=22) or both agents together [isosorbide mononitrate 40 mg and misoprostol 400 μg] ( n=22). Main outcome measures 1. To assess the cumulative force required to dilate the cervix to 8 mm; 2. the onset of new symptoms before termination of pregnancy. Results The cervical resistance following combination therapy with isosorbide mononitrate and misoprostol was not significantly different than following misoprostol alone [24.5N vs 18.5N; median difference (95% CI) 19N (-22 to 49)]. Pre-treatment with misoprostol used alone resulted in a lower cervical resistance than isosorbide mononitrate alone (18.5 N vs 39 N, P=0.04, Mann-Whitney U test). There was no difference in the number of women remaining asymptomatic following either isosorbide mononitrate or misoprostol or combination therapy [14/22 (64%) vs 11/21 (52%) vs 11/22 (50%), Fisher's exact test]. Conclusions We have not shown any advantage of combining misoprostol with the nitric oxide donor isosorbide mononitrate compared with misoprostol alone for pre-operative cervical ripening in the first trimester.