Papaverine prior to catheter balloon insertion for labor induction: a randomized controlled trial

Background Catheter-balloon insertion is a cervical ripening method of labor induction. Papaverine and its derivatives are musculotropic antispasmodic drugs that directly induce smooth muscle relaxation. Used during childbirth, these drugs have been suggested to shorten the duration of labor. Objective We aimed to evaluate the effect of administering papaverine prior to catheter-balloon insertion on changes in Bishop-scores and on the induction-to-delivery interval. Study Design This randomized double-blinded placebo-controlled trial was conducted in a single tertiary university-affiliated hospital. Participants were admitted at term for labor induction with an initial Bishop-score ≤6. Participants were randomized to receive papaverine intravenous 80 mg or saline 0.9%, within 30 minutes of Foley catheter-balloon insertion. The co-primary outcomes were the difference in Bishop-score from before catheter-balloon insertion to after removal, and the induction-to-delivery interval. Secondary outcomes included maternal pain and satisfaction-scores, delivery within 24-hours and neonatal outcome. Both intention-to-treat analysis and per protocol analysis were performed. Results In total, 110 women were enrolled. In the intention-to-treat analysis, for the papaverine (N=55) compared to the placebo group (N=55), the median (range) difference in Bishop-score was greater: 7 (range, 4-11) vs. 6 (1-11), p=0.023; and the median range catheter insertion-to-delivery interval was shorter: 21(6-95) vs. 26 (3-108) hours, p=0.031. A higher proportion of women in the papaverine than placebo group delivered within 24-hours: 65.5% vs. 41.8%, p=0.012. Pain and satisfaction-scores, delivery and neonatal outcomes were similar between the groups. Similar results were found in the per protocol analysis. Conclusions Papaverine prior to Foley-catheter insertion for cervical ripening resulted in improved Bishop-scores and shorter catheter-to-delivery intervals.