uterotonic

Uterotonic refers to a drug that stimulates contraction of the uterus. Uterotonics are used to prevent or treat postpartum hemorrhage and to induce or augment labor. They are distinct from tocolytics, which are used to suppress uterine contractions.

Mechanism and major agents: Uterotonics act by promoting myometrial contractions through various pathways. Oxytocin acts on oxytocin receptors to raise intracellular calcium and trigger contractions. Prostaglandins such as misoprostol (PGE1), dinoprostone (PGE2), and carboprost (PGF2α) promote uterine contractions and cervical ripening. Ergometrine/ergot alkaloids reach their effect by constricting uterine blood vessels and enhancing tone. Common agents include oxytocin, ergometrine, misoprostol, dinoprostone, and carboprost. They may be used alone or in combinations, depending on clinical goals and settings.

Clinical use and administration: Oxytocin is typically given by intravenous infusion or intramuscular injection to prevent postpartum hemorrhage after delivery or to induce/augment labor. Misoprostol can be given orally, sublingually, or vaginally and is favored in resource-limited settings for preventing or treating hemorrhage or for induction. Dinoprostone and carboprost are used selectively for induction or treatment of hemorrhage, with routes such as vaginal inserts, gels, or intramuscular injections. Ergometrine is often combined with oxytocin in formulations for active management of the third stage of labor, though it is used with caution in hypertensive patients.

Safety and considerations: Uterotonics carry risks including tachysystole (excessively frequent contractions), uterine rupture in scarred uteri, hypertension with ergometrine, and fever or diarrhea with prostaglandins. Some agents have contraindications or require caution in asthma, hepatic or renal impairment, or active fetal distress. Appropriate monitoring and dose adjustments are essential to balance efficacy with safety.