The Role of Cervical Ripening in Labor
Before labor can begin effectively, the cervix must undergo changes: it needs to soften, thin out (efface), and open (dilate) [1.2.2]. This preparatory process is known as cervical ripening. When labor needs to be started artificially—a process called induction—for medical reasons, the cervix may not be ready. In such cases, medications are often used to ripen the cervix and help initiate contractions [1.2.4].
Prostaglandins, which are hormone-like substances, play a natural role in this process [1.2.2]. Two of the most commonly used synthetic prostaglandins in a hospital setting are Cytotec and Cervidil [1.2.1]. While both serve a similar purpose, they differ in their chemical makeup, administration, FDA-approval status, and side effect profiles.
What is Cytotec (Misoprostol)?
Cytotec is the brand name for the drug misoprostol, a synthetic prostaglandin E1 analog [1.2.6]. Its original and only FDA-approved indication is for the prevention of gastric ulcers caused by NSAID medications [1.2.3, 1.4.3].
However, it is widely used "off-label" in obstetrics for cervical ripening and labor induction [1.4.5]. The term "off-label" means it is being used for a purpose not formally approved by the U.S. Food and Drug Administration (FDA) [1.4.1]. This practice is common in medicine when substantial clinical evidence supports a drug's effectiveness for an unapproved use.
Mechanism and Administration
Misoprostol works by softening and dilating the cervix and also causing uterine contractions [1.4.3]. It is available as an oral tablet, which can be administered either orally or by being placed directly in the vagina [1.9.3]. For labor induction, a small fragment of a tablet (typically 25 mcg) is used every four to six hours [1.2.6]. Because it's a tablet that gets absorbed, its effects cannot be quickly stopped once it has been administered [1.2.4, 1.9.3].
What is Cervidil (Dinoprostone)?
Cervidil is the brand name for dinoprostone, a medication that is chemically identical to the naturally occurring prostaglandin E2 (PGE2) [1.5.3]. Unlike Cytotec, Cervidil is specifically FDA-approved for the purpose of cervical ripening to induce labor in pregnant women at or near term [1.5.1, 1.5.2].
Mechanism and Administration
Cervidil is a vaginal insert that resembles a small piece of cardboard with a long string attached for retrieval [1.5.3]. The insert is placed in the posterior vaginal fornix and slowly releases dinoprostone over a 12-hour period [1.2.1, 1.5.3]. Its primary function is to soften and efface the cervix, though it may also cause mild contractions [1.2.2]. A key advantage of this system is that if any adverse reactions occur, such as excessive uterine contractions or fetal distress, the insert can be quickly and easily removed by pulling the string, which stops the medication delivery [1.2.1].
Head-to-Head Comparison: Cytotec vs. Cervidil
| Feature | Cytotec (Misoprostol) | Cervidil (Dinoprostone) |
|---|---|---|
| Active Ingredient | Misoprostol (Prostaglandin E1 analog) [1.2.6] | Dinoprostone (Prostaglandin E2) [1.5.3] |
| FDA Approval | Approved for stomach ulcers; used off-label for labor induction [1.4.5]. | FDA-approved for cervical ripening and labor induction [1.5.1]. |
| Administration | Oral or vaginal tablet fragment [1.9.3]. | Vaginal insert with a retrieval string [1.5.3]. |
| Reversibility | Cannot be easily reversed once absorbed [1.2.4]. | Can be quickly removed to stop drug delivery [1.2.1]. |
| Cost | Significantly less expensive [1.3.2, 1.3.3]. | More expensive [1.3.4]. |
| Time to Delivery | Often associated with a shorter time to delivery [1.3.2]. | May have a slower, more gradual induction process [1.2.1]. |
Risks, Side Effects, and Contraindications
Both medications carry risks and should only be administered in a hospital setting with continuous monitoring of both the mother and baby [1.2.1].
Uterine Tachysystole
A primary concern with both medications is uterine tachysystole, which is defined as excessive uterine contractions (typically more than five in 10 minutes) [1.2.6]. This can potentially affect blood flow to the baby and cause fetal distress [1.6.3]. Some studies suggest vaginal misoprostol carries a higher risk of tachysystole compared to dinoprostone, while other studies show oral misoprostol may have a lower risk [1.9.1, 1.9.5]. The ability to remove Cervidil is a significant safety advantage if tachysystole occurs [1.9.3].
Other Side Effects and Contraindications
Common side effects for both drugs can include fever, nausea, vomiting, and diarrhea [1.6.2].
These medications are generally contraindicated in patients with a history of a previous cesarean section or major uterine surgery due to an increased risk of uterine rupture [1.8.2]. Other contraindications include known hypersensitivity to prostaglandins, certain cases of fetal distress, and unexplained vaginal bleeding [1.8.2].
Conclusion
Cytotec and Cervidil are both effective prostaglandin-based medications used to prepare the cervix for labor induction. The primary differences lie in their FDA-approval status, cost, and administration method. Cervidil is an FDA-approved, removable vaginal insert that offers a controlled, reversible approach, though at a higher cost [1.2.1, 1.3.4]. Cytotec is a low-cost, effective, off-label option that acts quickly but cannot be stopped once administered [1.3.2, 1.4.5]. The choice between them depends on the clinical judgment of the healthcare provider, hospital protocols, and the individual patient's medical history and needs.
For more information from an authoritative source, you can visit the American College of Obstetricians and Gynecologists (ACOG) website at: https://www.acog.org/
