NO donors are superior to placebo or no treatment, but inferior to prostaglandins for first-trimester cervical ripening, and associated with more side effects.
A comparison of isosorbide mononitrate and misoprostol cervical ripening before suction evacuation.
To compare the efficacy of a nitric oxide donor (isosorbide mononitrate) and a prostaglandin E1 analogue (misoprostol) for cervical priming before suction termination of pregnancy.
                This was a randomized, double blind, placebo-controlled trial. One hundred twenty-six healthy women requesting termination of pregnancy between 9 and 12 weeks' gestation were recruited. Women were randomized into three groups: control, isosorbide mononitrate, and misoprostol. All women were given moistened intravaginal study drugs (placebo, 40 mg of isosorbide mononitrate, or 400 microg of misoprostol) 4-6 hours before suction evacuation. Side effects were assessed 3 hours after drug administration. The cervical dilatation and the cumulative force required to dilate the cervix to 8 mm were measured by a cervical tonometer before suction evacuation. Operative blood loss was measured after sieving off the products of gestation.
                There were no differences in the baseline cervical dilatation, cumulative force, and operative blood loss between the isosorbide mononitrate and placebo groups. However, women in the misoprostol group had a significantly greater cervical dilatation, required less cumulative force, and had less blood loss than women in the isosorbide mononitrate or control group. The majority (more than 80%) of women in all three groups found their cervical priming agents acceptable.
                Intravaginal isosorbide mononitrate was less effective than misoprostol in cervical ripening before suction termination of pregnancy.