The "PRIM" study: a randomized comparison of prostaglandin E2 gel with the nitric oxide donor isosorbide mononitrate for cervical ripening before the induction of labor at term.
OBJECTIVE
The purpose of this study was to compare the efficacy and safety profile of prostaglandin E2 with isosorbide mononitrate for cervical ripening before the induction of labor at term.


METHODS
Primigravid women were assigned randomly to receive either 40 mg of isosorbide mononitrate or 2 mg of prostaglandin E2. Efficacy outcomes were the cervical ripening effect of each agent and the time from treatment initiation to delivery. Safety outcomes were the incidence and frequency of maternal side effects and events that would be potentially hazardous for mother and baby during outpatient cervical ripening.


RESULTS
Prostaglandin E2 was more effective than isosorbide mononitrate in inducing a change in modified Bishop score. Mean duration from treatment initiation to delivery was greater for isosorbide mononitrate than prostaglandin E2. There were no adverse events in the isosorbide mononitrate group that would contraindicate outpatient treatment. However, in the prostaglandin E2 group, 7% of the pregnancies had abnormal fetal heart rate patterns (P = .0002). Maternal satisfaction was significantly higher in the isosorbide mononitrate group.


CONCLUSIONS
Although isosorbide mononitrate was less effective, maternal satisfaction was significantly greater. The safety profile of each agent was such that it would be reasonable to give isosorbide mononitrate, but not prostaglandin E2, on an outpatient basis.
Osman
Inass
I
Division of Developmental Medicine, University of Glasgow, Glasgow Royal Infirmary, United Kingdom.
MacKenzie
Fiona
F
Norrie
John
J
Murray
Heather M
HM
Greer
Ian A
IA
Norman
Jane E
JE
D000328:Adult; D020070:Cervical Ripening / Q000187:drug effects*; D015232:Dinoprostone; D004311:Double-Blind Method; D005260:Female; D005782:Gels; D006801:Humans; D007548:Isosorbide Dinitrate / Q000031:analogs & derivatives* / Q000627:therapeutic use; D007751:Labor, Induced; D020030:Nitric Oxide Donors / Q000627:therapeutic use*; D010120:Oxytocics; D011247:Pregnancy
D005782:Gels; D020030:Nitric Oxide Donors; D010120:Oxytocics; D007548:Isosorbide Dinitrate; D015232:Dinoprostone; C030397:isosorbide-5-mononitrate