Physiological context and problem
The normal course of the first stage of labor is based on synchronous processes. On the one hand, myometrial contractile activity increases; on the other hand, anatomical dilation of the cervix occurs.
However, in practice, physicians frequently encounter pathological conditions where cervical dilation lags behind. Such tissue rigidity or dystocia hinders normal fetal descent and requires mandatory medical intervention to accelerate labor.
Classification of pharmacological agents
To address delayed cervical dilation, the available agents are divided into two main groups:
- Drugs of choice (most commonly used) — prostaglandins (dinoprost, dinoprostone).
- Alternative agents (prescribed less frequently) — M-anticholinergics (e.g., atropine).
Differentiation from other myometrial agents
In clinical pharmacology, it is important to clearly distinguish between drugs that stimulate the birth canal and agents with the opposite effect:
- Stimulation of rhythmic uterine contractions: oxytocin, pituitrin, and dinoprost are used to enhance labor. It is important not to confuse them with tocolytics (atosiban, salbutamol), whose purpose is to suppress uterine contractions.
- Cessation of hypotonic hemorrhage: in the early postpartum period, oxytocin and ergometrine (ergot alkaloids) are used to induce strong tonic vascular contraction. In this situation, tocolytics are strictly contraindicated, as uterine relaxation will only increase bleeding.
Limitations of ergometrine use
Ergot derivatives, specifically ergometrine, have a powerful tonic effect on the myometrium, but have strict safety boundaries.
This agent is categorically not used for labor induction during pregnancy or during labor. The reason is the high risk of severe fetal hypoxia. This condition occurs due to an excessive increase in basal myometrial tone and disruption of normal uteroplacental blood flow.
Prostaglandins pave the way, oxytocin leads the uterus into battle, and ergometrine is used only postpartum to stop bleeding!
Class and exam questions
Which drugs are primary for stimulating cervical dilation?
The drugs of choice in this case are prostaglandins, such as dinoprost and dinoprostone.
Can ergometrine be used for labor induction?
No, ergometrine is not used for labor induction due to the risk of fetal hypoxia caused by impaired uteroplacental blood flow.
How do tocolytics differ from uterine contraction enhancers?
Tocolytics (e.g., atosiban, salbutamol, magnesium sulfate) suppress myometrial contractions, whereas oxytocin and dinoprost stimulate labor activity.
What alternative agents are used for cervical rigidity?
M-anticholinergics, such as atropine, are less frequently used as alternative agents.
What else to study on this topic
- Mechanisms of action of prostaglandins on the cervical connective tissue
- Comparative pharmacodynamics of dinoprost and dinoprostone
- Indications and contraindications for the prescription of M-anticholinergics in obstetrics
- Pharmacological differences between ergot alkaloids and oxytocin
- Pathogenesis of uteroplacental blood flow in tonic agent overdose
Master the entire topic in the «Pharmacology» course
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