Induction With Misoprostol: Oral Mucosa Versus Vaginal Epithelium (IMPROVE)

Misoprostol is currently administered in many different ways. It can be administered vaginally, rectally, orally, buccally, and sublingually. Each route has its benefits and potential drawbacks. While vaginal administration is most common, recent trends in practice have yielded more buccal use of this drug. There is extensive clinical experience with this agent and a large body of published reports supporting its safety and efficacy when used appropriately. However, we only found one published trial directly comparing buccal to vaginal misoprostol head-to-head. In that trial, there were no significant differences in any of the outcomes other than higher rates of tachysystole in the buccal group. However, this trial utilized higher doses of misoprostol (up to 100mcg) than are typically used clinically per the ACOG Practice Bulletin (starting at 25 mcg).

Additionally, there are few comparisons of the pharmacokinetics of misoprostol between the buccal and vaginal routes. In fact, all of the PK studies comparing these routes are in women undergoing pregnancy terminations in the 1st or 2nd trimesters and do not include women undergoing labor induction at term. As the physiological changes in pregnancy have a profound impact on drug metabolism and disposition, this is an important gap in the current knowledge.

The 3 Specific Aims of this trial are:

• To compare the efficacy and safety of 25 mcg of misoprostol initially followed by 50mcg thereafter administered by either buccal or vaginal route in a placebo-controlled, double blind RCT. We will recruit women at term undergoing labor induction to accomplish this trial.
• To compare the PK parameters of 25 mcg and 50 mcg of misoprostol administered by either buccal or vaginal routes. Further, we will analyze the clinical outcomes in Aim 1 based on the PK parameters, controlling for patient characteristics, to assess the impact of PK parameters on clinical success of this drug. In this way, we hope to comment on the strategic dose and individualized dosing model potential for labor induction with misoprostol.
• To compare the trial participant satisfaction with each route of administration to improve patient-based outcomes. This will be done by administering a satisfaction survey at the end of the trial. As participants will have study drug placed both buccally and vaginally, they will be uniquely able to comment on comfort and preference for route of delivery.

We will recruit women who are admitted for term labor induction and for whom the provider plans to utilize misoprostol. Women will be randomized to receive either buccal or vaginal misoprostol; first dose will be 25 mcg followed by 50mcg for subsequent doses. Three hundred women will be recruited to the overall trial and a subcohort of 60 women will be recruited to participate in the PK portion of the trial.

Inclusion criteria

• A medical indication for induction of labor at a gestational age between 37 +0 and 38 +6 weeks OR an elective or medical indication for induction of labor at a gestational age greater than or equal to 39 + 0 completed weeks
• Participant age of greater than or equal to14 years old
• Singleton pregnancy
• Modified Bishop score of less than or equal to 6
• Vertex fetal presentation by examination or ultrasound
• Any membrane status

Exclusion criteria

• Elective inductions between 37 +0 and 38 +6 completed weeks are specifically excluded
• Known intrauterine fetal demise
• Any uterine scar including prior cesarean section and myomectomy
• Known major fetal congenital malformations that may impact neonatal health
• Other evidence of fetal compromise (such as Category 2 or 3 tracing) before the induction begins
• Prior induction/cervical ripening methods utilized during this pregnancy
• Allergy to misoprostol
• Known untreated cervical infection (e.g. Gonorrhea, Chlamydia)
• Planned cesarean section due to maternal or fetal condition
• Any other contraindication to labor induction or misoprostol therapy