MISOBEST - Orally Misoprostol Solution (Cytotec®) Versus Orally Misoprostol as a Tablet (Angusta®) for Induction of Labor

In Sweden as in most other countries, the rate of induction of labor (IOL) has steadily increased, peaking at 27% of all deliveries in 2020. Due to recently published studies showing decreased perinatal mortality with IOL at 41 instead of 42 gestational weeks, national guidelines have changed to offering all pregnant women reaching 41 weeks IOL, which will increase induction rates and subsequent cost of IOL for medication further.

Spontaneous onset of labor is usually preferred, as it generally means lower risk of complications compared to IOL. If delivery needs to be induced in women with an unfavorable cervical status, an oral solution of misoprostol is a safe and inexpensive method that is easy to control and provides a high success rate of vaginal deliveries with a very low risk of hyper stimulation. Since the preparation of misoprostol (Cytotec®) has been used off-label with the solution being prepared locally at every unit, the profession has been looking for alternatives. Angusta® 25 ug tablets is the alternative that has been developed and approved but without being compared to the oral solution of misoprostol, the most commonly used method for IOL in Sweden. In addition, Angusta® is 43 times more expensive (1011 SEK compared to 23.60 SEK for Cytotec® for eight doses) considering "a typical induction" for primiparous women. Both methods are currently in use in clinical practice in Sweden.

A recent study conducted in Sweden 2020 shows that the Area Under the Curve (AUC) for the concentration in the blood of misoprostol after administration of 25 ug Cytotec® po compared to Angusta® 25ug po differs . The AUC is 32.9% higher with Cytotec® compared to Angusta®. The lower AUC for Angusta® may result in lower efficacy and time to delivery. However, this is unknown. The reason for this difference may be that a greater proportion of misoprostol is absorbed buccally and/or sublingually with use of misoprostol as a solution compared to when it is used as a tablet. Misoprostol has significantly different effect on uterine contractility depending on method of administration(1). Thus, using Angusta® may result in negative health economic outcomes due to higher price and in addition, a longer time spent in the delivery unit. No comparison of these two formulations has been performed in clinical practice.

Inclusion criteria

• Singleton gestations
• Cephalic presentation
• ≥37-42+0 weeks of gestation
• Unfavorable cervix score BS <6 in nulliparous women and <5 in parous women
• All participating women in the studies will receive oral and written information and must give informed consent before participation

Exclusion criteria

• Inability to understand the study information written in Swedish or English
• Previous hysterotomy (scar in the uterine myometrium)
• Non-reassuring cardiotocography (CTG) on admission (the door-test, first 20 minutes of registration of CTG).
• Hypersensitivity to the active substance
• If active labor has started
• When oxytocin infusion is already used
• Placenta previa
• Renal failure (GFR <15 ml/min/1.73 m2).
• Any condition or circumstance due to which the investigator considers it is not in the best interest of subject to participate in the study or the inclusion of a subject risks negatively impacting the scientific or ethical integrity of the clinical trial.