Nitric oxide donor isosorbide mononitrate for pre-induction cervical ripening at 41 weeks' gestation: A randomized controlled trial.
OBJECTIVE
Nitric oxide donors have been shown to cause cervical ripening. The aim of this study was to determine whether sustained release isosorbide mononitrate (ISMN-SR) 60 mg administered vaginally is effective for pre induction cervical ripening at 41 weeks' gestation.


METHODS
A double-blind randomised controlled trial was carried out at the University Obstetric Unit, Galle, Sri Lanka for a period of 9 months, commencing 1st August 2003. One hundred and fifty-six consecutive women with uncomplicated singleton pregnancies at 41 weeks' gestation with a modified Bishop Score <5 were allocated by stratified (primip/multip) block randomization to receive either ISMN-SR 60 mg (n = 78) or vitamin C 100 mg (n = 78) vaginally. Modified Bishop Score at 41 weeks + 2 days' gestation and the proportions establishing spontaneous labor or becoming favorable for induction of labor (IOL) by 41 weeks + 2 days' gestation were evaluated in each group.


RESULTS
At the commencement of the study there were no differences between the mean age, parity or modified Bishop Score of the two groups. In the ISMN-SR group, there was a marked increase in the proportion establishing spontaneous labor (28% vs 7.5%, P < 0.01) and being favorable for IOL (40% vs 9% P < 0.001), 2 days after therapy. In the ISMN-SR group, there was a significantly higher increase in the mean modified Bishop Score (3.8, 95% CI 2.3-5.3 vs 1.3, 95% CI 0.3-2.2, P < 0.01) and a marked decrease in the proportion of subjects requiring further ripening of the cervix with a Foley catheter. (32% vs 79%, P < 0.001). The cesarean section rates were similar in both groups.


CONCLUSIONS
Sustained release ISMN administered vaginally is effective for preinduction cervical ripening.
Rameez
Mohamed Furukan Mohamed
MF
Department of Obstetrics and Gynecology, Faculty of Medicine, University of Ruhuna, Galle, Sri Lanka.
Goonewardene
Indra Malik Rodrigo
IM
D000282:Administration, Intravaginal; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D020070:Cervical Ripening / Q000187:drug effects*; D003692:Delayed-Action Preparations; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007548:Isosorbide Dinitrate / Q000008:administration & dosage / Q000031:analogs & derivatives*; D020030:Nitric Oxide Donors / Q000008:administration & dosage*; D011247:Pregnancy
D003692:Delayed-Action Preparations; D020030:Nitric Oxide Donors; D007548:Isosorbide Dinitrate; C030397:isosorbide-5-mononitrate