Carbetocin Acetate

Uterine atony postpartum and after induced abortion is the primary cause of delayed uterine recovery and prolonged lochia. In severe cases, it may lead to complications such as postpartum hemorrhage and intrauterine infection, affecting maternal physical and mental health. As a long-acting oxytocic agent, carbetocin acetate binds specifically to oxystin receptors (OTR) on uterine smooth muscle, inducing potent and sustained rhythmic uterine contractions. It promotes myometrial repair, accelerates the expulsion of residual intrauterine tissue, shortens lochia duration, and improves postpartum recovery outcomes, leading to its widespread use in obstetric clinical practice.

Following normal delivery, the uterus requires sustained contraction to gradually return to its pre-pregnancy size, a process typically lasting 6–8 weeks. Uterine atony prolongs this process, manifesting as an enlarged uterus, slow descent of the uterine fundus, and prolonged, inefficient lochia discharge (normal lochia persists 4–6 weeks with a total volume of 250–500 mL). By activating oxystin receptors, carbansin induces rhythmic contractions of uterine smooth muscle, enhances myometrial tone, promotes myometrial cell repair and regeneration, and accelerates uterine involution.

Clinical studies demonstrate that postpartum administration of carbansin significantly shortens uterine involution time and reduces the incidence of uterine atony.

Compared with conventional oxystin, carbansin has a longer half-life (approximately 40 minutes vs. less than 10 minutes for oxystin) and a duration of action exceeding one hour. Single-dose administration achieves effective uterine contraction without continuous infusion, reducing clinical nursing workload and the risk of adverse reactions such as nausea, vomiting, and hypotension associated with prolonged infusion. In a cohort study of vaginal delivery patients, those receiving carbansin showed significantly faster uterine fundal descent at 24 hours postpartum, a higher rate of uterine volume restoration to pre-pregnancy levels by postpartum day 7, an average 2–3 day reduction in lochia duration, and no severe adverse events.

Oxystin receptors (OTR) are G protein-coupled receptors distributed in uterine smooth muscle, mammary glands, the central nervous system, and other tissues. Their activation triggers a series of signal transduction events involved in uterine contraction, lactation, mood regulation, and other physiological processes. As a selective OTR agonist, carbansin has high OTR affinity (Ki = 7.1 nm) and selectively activates OTR-related signaling pathways, making it an essential tool for studying OTR function and mechanisms.

In OTR signal transduction research, carbansin is commonly used to activate OTR and explore downstream pathway activation. Binding to OTR induces conformational changes, activating the Gq protein pathway and stimulating phospholipase C (PLC) to hydrolyze phosphatidylinositol 4,5-bisphosphate (PIP2) into the second messengers inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG).

IP3 binds to endoplasmic reticulum receptors, triggering intracellular calcium release and ultimately uterine smooth muscle contraction. Additionally, carbansin activates the Hippo/YAP pathway via OTR, promoting YAP translocation from the cytoplasm to the nucleus, regulating gene expression, and participating in myometrial cell proliferation and repair.

Carbansin is also used to study OTR localization, expression, and regulation. Fluorescently labeled carbansin enables intracellular OTR detection and mapping of tissue distribution under different physiological conditions. In OTR silencing or overexpression experiments, it acts as an agonist to verify the impact of OTR expression levels on function. Studies have also explored its non-obstetric roles, including central nervous system effects: carbansin crosses the blood-brain barrier to activate central OTR, exerting antidepressant-like effects and providing new insights for psychiatric research.

The efficacy and safety of obstetric hemostatic agents directly impact maternal outcomes. Commonly used agents include oxystin, ergometrine, and carboprost tromethamine. As a long-acting oxytocic, carbansin is frequently used in comparative studies and as a positive control in new drug development, providing benchmarks for evaluating efficacy and safety.

Multiple randomized controlled trials show carbansin is comparable to conventional oxystin in preventing postpartum hemorrhage and promoting uterine contraction, with a longer duration, easier single-dose administration, and lower adverse reaction rates.

A meta-analysis of 11 randomized controlled trials (2,635 women) found intramuscular carbetocin acetate was non-inferior to oxystin in reducing severe bleeding, with lower additional uterotonic use after cesarean section. Compared with ergometrine, it reduced bleeding after vaginal delivery and significantly lowered the incidence of nausea, vomiting, hypertension, and other adverse reactions, demonstrating superior safety. These studies support optimized obstetric hemostatic strategies.