Oral Misoprostol Found Slower but Cheaper For Labor Induction

OB/GYN News, August 15, 2000 by Sherry Boschert

SAN FRANCISCO - Vaginally administered misoprostol induced labor and delivery as quickly as dinoprostone plus oxytocin and beat oral misoprostol in two separate studies.

However, compared with drugs delivered vaginally, oral misoprostol is more convenient and inexpensive--costing mere cents per dose rather than several dollars per dose--investigators said at the annual meeting of the American College of Obstetricians and Gynecologists.

In the first study, 152 patients undergoing labor induction were randomly assigned to receive intravaginal dinoprostone (Cervidil) or oral or intravaginal misoprostol, neither forms of which have been approved for labor induction, but both of which are used off label by physicians.

More women delivered vaginally using oral or vaginal misoprostol (86% and 87%, respectively), compared with the dinoprostone group (79%), said Dr. Jennifer Goedken of the University of Massachusetts in Worcester.

However, women taking oral misoprostol took 6 hours longer to reach delivery after starting the drug, compared with women using either of the intravaginal medications.

The time to delivery for women in the oral misoprostol averaged 26 hours, compared with 20 hours using either vaginal. medication.

Women in the oral misoprostol group took 50 [micro] plus placebo every 4 hours for 24 hours, with an optional additional dosage of 50 [micro]g after the second dosage, the investigators said.

Women in the intravaginal misoprostol group received 25 [micro]g plus an oral placebo every 4 hours for 24 hours, with an optional oral placebo after the second dosage.

Both of the groups in the study were given oxytocin if needed for up to 24 hours.

And women in the dinoprostone group received 10 mg and oxytocin up to 48 hours or oxytocin alone if the Bishop's score was 5 or higher.

Misoprostol was associated with more tachysystole (16% for oral and 20% for intravaginal administration) than was dinoprostone/oxytocin (2%), but rates of hyperstimulation were similar among the groups: 4%, 7%, and 20/a, respectively.

It was hoped that the study would show that oral misoprostol was as effective as vaginal administration.

"Unfortunately it's not," she conduded.

Yet the convenience and patient satisfaction with oral misoprostol make it good enough to offer it to women as a treatment option,. Dr. Joseph Browning noted in a separate poster presented at the meeting.

Physicians need a deft hand to place a tiny misoprostol tablet in the posterior vagina, and the intravaginal route is more invasive for patients than taking a pill with a sip of water, Dr. Browning observed.

Oral misoprostol 50 [micro]g was as effective as intravaginal dinoprostone 4 mg in a randomized study of 60 patients undergoing labor induction, said Dr. Browning of Portsmouth (Va.) Naval Hospital. Patients were given a maximum of six doses of either drug plus subsequent intravenous oxytocin.

The mean interval from start of induction to delivery was similar between groups: 1,495 minutes with oral misoprostol and 1,692 minutes with dinoprostone, he added.

Vaginal delivery occurred within 24 hours among 46% of patients given misoprostol and 37% of patients using dinoprostone.

Patients in both groups used an average of three doses each.

There were no significant differences between groups in rates of tachysystole, uterine hyperstimulation, or fetal heart rate changes.

Findings from a third study caution against using dinoprostone as a preinduction cervical ripening agent on an outpatient basis.

In the uncontrolled trial, 111 patients inserted a single intravaginal sustained-release 0.3 mg/hour dosage of dinoprostone.

Regular contractions ensued within 12 hours in 26 patients (24%), Dr. Shaun Tassone reported in a separate poster presentation.

The dinoprostone insert had to be removed after about 6 hours because of active labor in 19 patients, ruptured membranes in 5, uterine tachysystole in 5, and nonreassuring fetal heart rates in 2 patients. The insert fell out on its own in six patients (5%).

The high rate of initiating regular uterine contractions and the frequent need to remove the vaginal insert within 12 hours makes inpatient use preferable to outpatient use for cervical ripening, said Dr. Tassone of the University of Oklahoma in Oklahoma City.

Cervidil's package insert specifies that the product is to be used on inpatients only.