A Relative Bioavailability Study of Two Misoprostol Formulations Following a Single Oral or Sublingual Administration

Trends and regional variations in prescriptions dispensed to stimulate uterine contractions at the end of pregnancy in Belgium: A community-based study from 2003 to 2018

PURPOSE

To investigate trends and regional variations in uterotonics dispensed around birth between 2003 and 2018 in Belgium.

METHODS

Data, including outpatient and inpatient prescriptions were extracted from a nationally representative prescription database. The prevalence of uterotonics dispensed during a period including the 7 days before birth, the delivery day and the 7 days after birth was computed over three 4-year-long study periods from 2003 to 2018. The trends between periods and associations between the use of at least one uterotonic and maternal age, region of residence, delivery type and social status were assessed using logistic regression.

RESULTS

In total, 31 675 pregnancies were included in the study. The proportion of pregnancies exposed to at least one uterotonic decreased significantly from 92.9% (95%CI, 92.3-93.4) in 2003-2006 to 91.4% (95%CI, 90.7-92.0) in 2015-2018 for vaginal births and from 95.5% (95%CI, 94.5-96.4) to 93.7% (95%CI, 92.6-94.7) for caesarean sections. However, for vaginal births, the proportion of oxytocin increased from 84.5% (95%CI, 83.7-85.2) to 89% (95%CI 88.3-89.7). A significant association was found between uterotonic agent use and maternal age, region of residence, and delivery type. The dispensation of some uterotonic agents differed significantly between the regions.

CONCLUSIONS

The proportion of pregnancies exposed to at least one uterotonic was high across the study period but decreased slightly between 2003 and 2018. Important variations in uterotonic use between regions highlight the need for improved national guidance.

Sublingual misoprostol vs. oral misoprostol solution for induction of labor: A retrospective study

Introduction

Induction of labor (IOL) is one of the most common obstetrical procedures, with an increasing rate. The prostaglandin E1 analogue misoprostol is frequently used as a primary method of labor induction. The optimal dose and route of administration is yet to be ascertained.

Aim

To compare efficiacy and safety between a regimen of sublingually administered misoprostol and a regimen of orally administered misoprostol, with cesarean delivery as primary outcome.

Methods

A retrospective study was conducted including women carrying a live, singleton fetus in a cephalic position with labor induced at >37 + 0 gestational weeks at Skåne University hospital, Lund, between January 1st 2013 to December 31st 2017. Data was obtained from computerized obstetrical charts.

Results

Totally 2,404 women were included; 974 induced with sublingual misoprostol and 1,430 with oral solution. In primiparous women the cesarean delivery rate was lower in primiparous women induced with oral compared to sublingual misoprostol (20.5% vs. 28.6%, p < 0.001), whereas in parous women the rates did not differ significantly 4.9% vs. 7.5%; NS). The increased risk of caesarean remained after controlling for potential confounding factors (adjusted odds ratio 1.49 (1.14–1.95). Women induced with sublingual misoprostol had a shorter time to vaginal delivery when compared to oral solution (primiparous median 16.7 h vs. 21.7 h; p < 0.001, parous median 9.9 h vs. 13.3 h; p = 0.01), and a higher rate of vaginal delivery within 24 h (primiparas 77.7% vs. 63.3%, p < 0.001, parous 93.2% vs. 84.2%; p = 0.01).

Conclusion

IOL with oral misoprostol solution was associated with a significantly higher vaginal delivery rate when compared to sublingual misoprostol, whereas sublingual misoprostol was associated with a significantly shorter time from induction to vaginal delivery. Oral administration is considered the most safe and efficient administration of misoprostol, although more studies are needed to find the optimal route and dosage of misoprostol for IOL.

Pharmacokinetics of Vaginal vs Buccal Misoprostol for Labor Induction at Term

The IMPROVE study (NCT02408315) compared the efficacy and safety of vaginal and buccal administration of misoprostol for full‐term, uncomplicated labor induction. This report compares the pharmacokinetics of misoprostol between vaginal and buccal routes. Women greater than or equal to 14 years of age undergoing induction of labor greater than or equal to 37 weeks gestation without significant complications were randomized to vaginal or buccal misoprostol 25 μg followed by 50 μg doses every 4 h. Misoprostol acid concentrations were determined using liquid chromatography‐tandem mass spectrometry for the first 8 h in a subgroup of participants. A population pharmacokinetic model was developed using NONMEM. Plasma concentrations (n = 469) from 47 women were fit to a one‐compartment nonlinear clearance model. The absorption rate constant (k_a) was dependent on both route and dose of administration: buccal 25 μg 0.724 (95% confidence interval, 0.54–0.92) h⁻¹; 50 μg 0.531 (0.37–0.63) h⁻¹; vaginal 25 μg 0.507 (0. 2–1. 4) h⁻¹; and 50 μg 0.246 (0.103–0.453) h⁻¹. Relative bioavailability for vaginal compared to buccal route was 2.4 (1.63–4.77). There was no effect of body mass index or age on apparent clearance 705 (431–1099) L/h or apparent volume of distribution 632 (343–1008) L. The area under the concentration–time curve to 4 h following the first 25 μg dose of misoprostol was 16.5 (15.4–17.5) pg h/ml for buccal and 34.3 (32.5–36.1) pg h/ml for vaginal administration. The rate of buccal absorption was two times faster than that of vaginal, whereas bioavailability of vaginal administration was 2.4 times higher than that of buccal. Decreased time to delivery observed with vaginal dosing may be due to higher exposure to misoprostol acid compared to buccal.

Oral misoprostol tablets (25 µg) for induction of labor: a targeted literature review and cost analysis

BACKGROUND

Various methods exist for the induction of labor (IOL), and there is limited consensus as to optimal methods. Off-label misoprostol is recommended by the World Health Organization (WHO) for IOL but preparing it into doses suitable for IOL lacks precision, with potential adverse outcomes if dosing is inaccurate. This study explores potential outcomes and costs associated with increased uptake of a low-dose (25 µg) oral misoprostol formulation (Angusta; Norgine BV, Amsterdam) approved for IOL, in France, Belgium, and the Netherlands.

METHODS

A literature review was undertaken to derive probabilities of delivery outcomes (vaginal, instrumental, and cesarean sections) for IOL methods, from published meta-analyses. Outcomes for oral misoprostol tablets (25 µg) were unavailable in the meta-analyses, so were estimated using data from two published retrospective cohort studies. A model was developed to predict the frequency of IOL outcomes and associated costs at the national level, across multiple scenarios. Scenarios were tested using a moderate, medium, and high increase in oral misoprostol tablet (25 µg) uptake. Market shares, costs, and induction rates were defined for each country using multiple data sources.

RESULTS

Increased uptake of oral misoprostol tablets (25 µg) was estimated to be associated with a slightly increased rate of routine vaginal deliveries, and concurrent decreases in instrumental vaginal deliveries and cesarean sections. Since routine vaginal deliveries are less costly than other delivery outcomes, increased uptake of oral misoprostol tablets (25 µg) within the IOL market has the potential to be cost-saving. These trends were predicted using 25 µg oral misoprostol tablet outcomes informed by both retrospective studies.

CONCLUSION

Preliminary outcomes suggest that oral misoprostol tablets at 25 µg per dose may improve outcomes in IOL and be cost-saving. Further study is required to validate these findings and assess the comparative efficacy of IOL methods, including oral misoprostol tablets (25 µg).