145: Randomized clinical trial of cervical ripening and labor induction using oral misoprostol with or without intravaginal isosorbide mononitrate


      To determine the efficacy of the addition of intravaginal isosorbide mononitrate (IMN) to an established protocol of oral misoprostol (miso) for cervical ripening and labor induction.

      Study Design

      A prospective, randomized trial was conducted. Women scheduled for labor induction between 32 and 42 weeks and with unfavorable cervices (Bishop score ≤ 6) were randomized to receive miso every 4 hours up to 4 doses with or without IMN every 6 hours up to 2 doses. A strict ripening and induction protocol including timing of oxytocin use and amniotomy was used. Subjects were evaluated for side effects 6 hours after study initiation. The study was powered to detect a primary endpoint of a change in time to vaginal delivery (VD) of 4 hours (α=.05 and β=.20). Student t, Chi-square, Fisher's exact and Mann-Whitney tests were used where appropriate with p < .05 deemed significant.


      155 women were randomized; 2 were excluded after randomization. 78 women received miso, and 75 women received miso with IMN. There were no demographic differences between groups. Results are shown in the table. There was no reduction in the primary outcome of time to VD with the addition of IMN to miso. Cesarean delivery (CD) rates were similar in both arms, as were rates of contraction abnormalities and fetal heart rate abnormalities (abnl FHR). Subjects receiving miso with IMN experienced similar rates of nausea, diarrhea, flushing and dizziness as those receiving miso alone but reported headache more often.
      Tabled 1Miso +/− IMN Outcomes
      MisoMiso with IMNp-value
      Median hrs to VD17.818.8.69
      CD18 (23%)22 (29%).31
      Tachy-systole8 (10%)6 (8%).31
      Abnl FHR28 (36%)37 (49%).09
      Headache12 (15%)52 (69%)<.001


      The addition of intravaginal IMN to oral miso for cervical ripening and labor induction did not significantly reduce time to VD and was associated with a greater incidence of headache.