Carbetocin (Duratocin / Pabal)

Prescription

Carbetocin is a synthetic analog of oxytocin engineered for a longer duration of action, used to prevent excessive bleeding after childbirth (postpartum hemorrhage). Oxytocin itself is the standard uterotonic given at delivery to make the uterus contract and clamp down on the blood vessels that fed the placenta, but its very short half-life means it is usually given as a continuous infusion. Carbetocin's structural modifications — a deaminated first residue and an O-methyl-tyrosine substitution, with a stable carba bridge replacing oxytocin's disulfide bond — resist enzymatic breakdown, so a single injection produces sustained uterine contraction lasting roughly an hour. Mechanistically carbetocin acts like oxytocin: it binds oxytocin receptors on uterine smooth muscle, triggering rhythmic and then sustained (tetanic) contractions of the postpartum uterus. This mechanical compression of the uterine vasculature is what limits blood loss. Because one injection replaces an infusion, carbetocin simplifies the third stage of labor, particularly at cesarean delivery, where it is widely used. A landmark development was a heat-stable formulation of carbetocin, which — unlike oxytocin — does not require refrigeration. The World Health Organization has recognized heat-stable carbetocin as an option for preventing postpartum hemorrhage where a reliable cold chain is difficult, an important consideration in many low- and middle-income countries where postpartum hemorrhage is a leading cause of maternal death. Carbetocin is approved in the EU, UK, Canada, Australia, and many other countries, but it is not FDA-approved in the United States, where oxytocin remains standard. Side effects overlap with oxytocin — nausea, flushing, headache, hypotension, and abdominal pain — and it is contraindicated for inducing or augmenting labor (it is used only after delivery). Its use is confined to obstetric care by trained clinicians.