Pharmacodynamics and key effects
Prostaglandin-based drugs have a pronounced stimulating effect on the myometrium. Under their influence, the smooth muscle of the uterus begins to contract rhythmically, and its baseline tone increases significantly and stably.
The most important pharmacological feature of prostaglandins is their temporal universality. Unlike oxytocin, to which the uterus becomes sensitive only in the late stages of gestation, prostaglandins work effectively at all stages of pregnancy.
In addition, they have a specific effect on the cervix: they cause its relaxation, effacement, and dilatation (this process is clinically referred to as "ripening"). Due to this dual effect (active stimulation of the uterine body and parallel relaxation of the cervix), these agents are successfully used both for elective labor induction and for medical termination of pregnancy.
The pharmacokinetics of the drugs is characterized by rapid metabolism. They are very quickly inactivated in the pulmonary vascular bed, as well as in the tissues of the kidneys, spleen, intestines, and adipose tissue. The half-life is so short that upon intravenous administration, 97% of PGE_2 disappears without a trace from blood plasma in just 90 seconds.
Dinoprost (PGF2α analogue)
Dinoprost (known under the trade name Enzaprost-F) is a PGF_{2\alpha} prostaglandin preparation. It reliably stimulates the myometrium at any gestational age and promotes cervical effacement.
Main indications and routes of administration:
- Medical abortion: up to 15 weeks of gestation, the drug is administered intra-amniotically (directly into the amniotic sac), and after 15 weeks, extra-amniotic administration is used.
- Labor dystocia (weak labor): used as intravenous drip infusions to enhance contractions.
Characteristic side effects:
- Respiratory system: the drug increases pulmonary vascular tone and can provoke bronchospasm. For this reason, it is prescribed with extreme caution to female patients suffering from bronchial asthma.
- Gastrointestinal tract: a sharp increase in motility is observed, often leading to diarrhea.
- Cardiovascular system: pronounced blood pressure fluctuations are possible (at high doses, the drug causes hypertension) and various cardiac arrhythmias.
Dinoprostone (PGE2 analogue)
Dinoprostone (also known as Prostenon, Prostin E_2) is a synthetic analogue of prostaglandin PGE_2.
Its stimulating effect on the uterus and gastrointestinal tract is largely similar to the effects of dinoprost, but its influence on other body systems is radically different:
- Respiratory system: unlike dinoprost, dinoprostone dilates the bronchial lumen and pulmonary vessels, acting as a bronchodilator.
- Hemodynamics: has a noticeable hypotensive effect, meaning it lowers blood pressure.
Indications and dosage forms: For labor induction, the drug may be prescribed orally, via intravenous infusion, or intravaginally (in the form of a special gel). For medical abortion, exclusively intravenous infusions are used.
Specific side effects: In addition to standard nausea, vomiting, diarrhea, headache, and hypotension, dinoprostone actively affects thermoregulation. It directly stimulates the corresponding center in the hypothalamus, causing patients to experience severe chills and elevated body temperature.
Complications and emergency care
The main risk of using any prostaglandin preparations is the development of hyperstimulation (excessive, uncontrolled stimulation of myometrial contractions). Excessive and prolonged uterine activity critically disrupts placental and uterine blood flow, creating a direct threat of acute fetal hypoxia.
Emergency management algorithm for hyperstimulation:
- Immediate discontinuation: completely stop the administration of the drug.
- Removal of the drug: if local forms were used (e.g., vaginal gel), it is necessary to thoroughly remove the drug residue from the vagina.
- Supportive therapy: initiate oxygen therapy to combat hypoxia.
- Pharmacological correction: intravenously administer drugs from the $\beta_2$-adrenomimetic group to rapidly relax the myometrium.
Briefly: answers to topical questions
Which specific beta2-adrenomimetic drugs are used to relieve uterine hypertonus during prostaglandin overdose?
To relieve uterine hypertonus during prostaglandin overdose, $\beta_2$-adrenomimetics are used, which induce myometrial relaxation. Specific drugs of this group with a tocolytic effect include:
- Salbutamol — exerts its effect through direct stimulation of myometrial $\beta_2$-adrenergic receptors, suppressing its contractions.
- Fenoterol — a $\beta_2$-adrenomimetic that also induces tocolysis and is used for uterine relaxation.
To easily remember the difference in side effects: dinoprostON (PGE2) — Opens (dilates bronchi and lowers BP), while dinoprost (PGF2α) — spasms (causes bronchospasm and increases pressure).
Class and exam questions
What is the main difference between prostaglandins and oxytocin?
Myometrial sensitivity to prostaglandins does not depend on gestational age, which is why they effectively stimulate the uterus at any stage of pregnancy, whereas oxytocin works predominantly in late terms.
Why is dinoprost dangerous for patients with bronchial asthma?
This drug causes an increase in the tone of the bronchial smooth muscle and pulmonary vessels, which can provoke a severe asthma attack.
Where do chills come from upon administration of dinoprostone?
Dinoprostone is capable of directly stimulating the thermoregulatory center located in the hypothalamus, leading to elevated body temperature and the onset of chills.
What else to study on this topic
- Regimens of intra-amniotic and extra-amniotic administration of dinoprost
- Pharmacokinetics of prostaglandins in various tissues (kidneys, spleen, adipose tissue)
- Mechanisms of fetal hypoxia development during myometrial hypertonus
- Comparative characteristics of dinoprostone dosage forms (gel, infusions, tablets)
Master the entire topic in the «Pharmacology» course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Prostaglandins affecting the myometrium" and 5,304 more subject pages
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 116 video lessons on the subject
Other topics in the section "Drugs affecting myometrial tone and contractile activity"
Free video lessons: pharmacologyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.