Isosorbide mononitrate followed by misoprostol compared with misoprostol alone for induction of labour at term: a randomized controlled trial

Abstract

Background: The rate of induction of labour is on rise globally due to various indications. The use of well established methods for induction of labour like prostaglandins is associated with various maternal and fetal adverse effects. Objective: Present study was designed to investigate the efficacy and safety of Nitric Oxide (NO) donor, Isosorbide mononitrate (ISMN) for cervical ripening and labour induction. To see the effect of sequential use of ISMN followed by misoprostol compared to misoprostol alone on induction of labour at term. Methods: This prospective randomized controlled trial was conducted from May 2012 to April 2013. Total 100 women, who fulfilled the inclusion criteria were admitted for labor induction during the study period. Study group received 60 mg sustained release tablet of Isosorbide mononitrate (ISMN) and control group received placebo, per vaginally, for cervical ripening. Bishop score was reassessed after 16 hours and participants in each group received 25mcg of misoprostol tablet per vaginally at 4 hrs interval for maximum of 4 doses till 3 contraction in 10 min or if cervix was dilated 3cm or more. Progress of labor was monitored using partograph. Results: There was significant difference between ISMN group and control group with respect to mean Bishop score (5.5±0.54 verses 4.16±0.76, p value <0.001). Vaginal delivery were more in ISMN group (66% vs 32%), so caesarean section were less in ISMN group ( 34% vs 68%, p=0.46). Lesser doses of misoprostol was required in ISMN group and reduced requirement of oxytocin to achieve vaginal delivery in ISMN group as compared to control group (9.1% vs 81.25%, p=0.001). Induction to vaginal delivery interval less than 12 hrs was seen on 54% cases in study group whereas none patient delivered in this interval in control group which was statistically significant ( p=0.0002). Major side effect of ISMN was headache which responded to analgesia. Conclusion: ISMN is an ideal agent for effective cervical ripening, which induces ripening of cervix without causing uterine contraction. It significantly improves mean Bishop score, reduces the number of misoprostol doses required to achieve vaginal delivery and less induction failure.

Keywords

• isosorbide mononitrate (ismn)
• no donors (nitric oxide donors)