Carbetocin
Also known as: Carbetocin Acetate · Pabal (brand) · Duratocin (brand) · Lonactene (brand)
Carbetocin is a synthetic, long-acting analog of oxytocin, modified specifically to resist the rapid enzymatic degradation that gives native oxytocin a circulating half-life of only about 3.4 minutes — Carbetocin's modifications extend this to roughly 85-100 minutes. At Verified Peptides, we want to note a genuine regulatory-history point: Carbetocin has been approved internationally for decades (as Pabal in the EU, Duratocin in Canada) for preventing postpartum hemorrhage after cesarean section, but has not been FDA-approved for use in the United States. We also think a heat-stable formulation of Carbetocin represents a genuinely important global health development: the WHO-led CHAMPION trial (Widmer et al. 2018, PMID 29949473, New England Journal of Medicine), an international trial across 23 hospitals in 10 countries, found heat-stable Carbetocin noninferior to oxytocin for preventing postpartum hemorrhage — critically, without requiring the cold-chain refrigeration that oxytocin needs, addressing a major real-world barrier to postpartum hemorrhage prevention in regions without reliable refrigeration. Research-grade material sold here is a separate product intended solely for laboratory research.
What is Carbetocin?
Carbetocin is a synthetic analog of oxytocin, the naturally occurring nonapeptide hormone involved in uterine contraction during labor and milk ejection during lactation, also built on this site. Carbetocin carries two specific modifications relative to native oxytocin: a 1-deamino modification (removing the free amino group at the N-terminal cysteine-derived residue) and an O-methylation at the tyrosine residue at position 2, combined with cyclization via a stable thioether linkage in place of oxytocin's native disulfide bond.
At Verified Peptides, we want to explain why these specific modifications matter clinically: native oxytocin is rapidly degraded in circulation, primarily by aminopeptidases (which the 1-deamino modification specifically resists, since removing the free amino group eliminates the primary site these enzymes act on) and by disulfide-cleaving enzymes (which the thioether-based cyclization, rather than a native disulfide bond, is inherently resistant to). Together, these modifications extend Carbetocin's circulating half-life to approximately 85-100 minutes, compared to native oxytocin's half-life of only about 3.4 minutes — a roughly 25-to-30-fold stability improvement that makes single-dose administration clinically practical for sustained uterotonic effect, rather than requiring the continuous intravenous infusion typically needed to maintain therapeutic oxytocin levels.
Chemically, Carbetocin has molecular formula C45H69N11O12S, molecular weight approximately 988.17 g/mol (independently cross-calculated atom-by-atom from the formula, matching literature figures exactly), CAS number 37025-55-1 (free base; acetate salt CAS 1631754-28-3), PubChem CID 16681432. We want to directly note a genuine regulatory distinction: Carbetocin has been approved for decades in the European Union (as Pabal), Canada (as Duratocin), and numerous other countries for preventing postpartum hemorrhage after cesarean section, but has not received FDA approval for use in the United States.
We independently cross-calculated Carbetocin's molecular weight atom-by-atom from its formula (45 carbon at 12.011, 69 hydrogen at 1.008, 11 nitrogen at 14.007, 12 oxygen at 15.999, and 1 sulfur at 32.06), arriving at approximately 988.17 g/mol, matching vendor- and literature-reported figures exactly, giving us confidence in these chemical identifiers without needing to flag any discrepancy, similar to the clean checks we performed for several other compounds in this phase.
Key Benefits & Mechanisms
Mechanism of action
Carbetocin acts as an agonist at the oxytocin receptor, the same receptor targeted by native oxytocin, with selectivity favoring the oxytocin receptor over the related vasopressin V2 receptor. Oxytocin receptor activation on uterine smooth muscle cells triggers a signaling cascade (involving increased intracellular calcium) that produces sustained uterine contraction, the therapeutic basis for Carbetocin's use in preventing excessive postpartum bleeding, since sustained uterine contraction after delivery helps compress the blood vessels at the placental attachment site and limit blood loss.
Carbetocin's extended half-life, discussed in the previous section, is specifically what allows a single intravenous or intramuscular dose to provide sustained uterotonic activity through the critical postpartum period, in contrast to native oxytocin, which requires continuous infusion to maintain comparable sustained effect given its very short half-life. We want to note that Carbetocin is also reported to be a functionally selective ('biased') oxytocin receptor agonist at the level of downstream signaling, with research indicating it promotes receptor internalization through a distinct pathway compared to native oxytocin, without the same degree of receptor recycling — a molecular pharmacology detail of ongoing research interest that may relate to differences in the duration and pattern of receptor signaling between the native hormone and this synthetic analog, beyond simply extended half-life alone.
Beyond its direct uterotonic effect, oxytocin receptor signaling more broadly is also implicated in social bonding, trust, and affiliative behavior research, an area more prominently discussed on this site's Oxytocin profile — Carbetocin, as a peripherally-focused obstetric drug developed and studied almost exclusively for its uterotonic effect, has a much more limited independent research literature specifically addressing these central nervous system or behavioral dimensions of oxytocin receptor activity, a distinction worth understanding when comparing the two compounds' respective research scopes.
Research Summary
At Verified Peptides, we think Carbetocin has a substantial and genuinely important clinical evidence base, including one of the largest and most globally significant trials of any compound in this catalog. The key large-scale trial is Widmer et al. (2018, New England Journal of Medicine, PMID 29949473, volume 379, issue 8, pages 743-752), the WHO-led CHAMPION trial, an international, randomized, double-blind, active-controlled noninferiority trial conducted at 23 hospitals across 10 countries (Argentina, Egypt, India, Kenya, Nigeria, Singapore, South Africa, Thailand, Uganda, and the United Kingdom), comparing a heat-stable formulation of Carbetocin against oxytocin for preventing postpartum hemorrhage after vaginal birth. The trial found heat-stable Carbetocin noninferior to oxytocin for preventing blood loss of at least 500 mL or the need for additional uterotonic agents, though noninferiority was not established for the more severe outcome of blood loss of at least 1000 mL.
We want to be direct about why this trial matters beyond its efficacy findings alone: postpartum hemorrhage is the leading cause of maternal death worldwide, and standard oxytocin requires cold-chain refrigeration that is unavailable in many lower-resource settings, creating a genuine, practical barrier to reliable postpartum hemorrhage prevention independent of any drug's inherent efficacy. Heat-stable Carbetocin's noninferiority to oxytocin, combined with its ability to remain stable without refrigeration, directly addresses this real-world implementation barrier, which is part of why the World Health Organization has specifically recommended heat-stable Carbetocin as an option for postpartum hemorrhage prevention in settings where maintaining an oxytocin cold chain is not feasible.
An earlier, smaller trial (Attilakos et al. 2010, BJOG, PMID 20482535, volume 117, issue 8, pages 929-936), a double-blind randomized trial at a UK teaching hospital, compared standard (non-heat-stable) Carbetocin against oxytocin after cesarean delivery, finding significantly fewer Carbetocin-treated women required additional uterotonic medications (33.5% versus 45.5%), though no significant difference was found in rates of severe hemorrhage, transfusion requirements, or hemoglobin decline between groups. At Verified Peptides, we sell research-grade Carbetocin exclusively for laboratory research.
Common Stacks
Lesser-Known Facts About Carbetocin
Carbetocin's development reflects a broader pattern seen repeatedly across this catalog: several native peptide hormones with clinically useful biological activity (native GnRH, native somatostatin, native oxytocin) share an extremely short circulating half-life that makes the unmodified native hormone clinically impractical, requiring synthetic modification specifically targeting the enzymatic degradation pathway responsible for that instability — in Carbetocin's case, aminopeptidase resistance via the 1-deamino modification and disulfidase resistance via thioether cyclization, distinct from the specific stabilization strategies used for GnRH agonists or somatostatin analogs elsewhere in this catalog, but conceptually addressing the same general problem.
The heat-stable formulation of Carbetocin specifically used in the WHO CHAMPION trial represents a genuinely significant pharmaceutical formulation achievement independent of the peptide's own chemical stability, since maintaining product stability without refrigeration across the temperature and humidity ranges found in many lower-resource healthcare settings requires careful attention to formulation excipients and packaging, not merely the underlying peptide's intrinsic degradation resistance.
Carbetocin's approval specifically for cesarean section, rather than for all deliveries generally, in several of its earliest approved markets reflects the specific patient population (women undergoing planned or urgent surgical delivery) in which its original pivotal trials were conducted, illustrating how a drug's approved indication can initially reflect the specific population studied in pivotal trials before later evidence (such as the CHAMPION trial's focus on vaginal birth) supports broader use.
Purity & Sourcing Considerations
At Verified Peptides, we require independent third-party HPLC purity testing and mass spectrometry identity confirmation for every batch of research-grade Carbetocin we offer, with a Certificate of Analysis (COA) available for each lot. As a peptide with a thioether cyclization (rather than the disulfide cyclization used in native oxytocin and several other cyclic peptides in this catalog), correct formation of this specific linkage should be confirmed as part of identity testing.
We source exclusively from manufacturers operating under Good Manufacturing Practice (GMP)-aligned quality systems, and every lot is independently verified rather than accepted solely on a supplier's internal documentation. Researchers should always request and review the specific COA for the lot they receive, confirming purity percentage and molecular identity before use in any experimental protocol.
Storage & Stability
Lyophilized Carbetocin is stable when stored at -20°C, protected from light and moisture. At Verified Peptides, we ship lyophilized peptide with appropriate cold-chain packaging to preserve stability in transit.
Once reconstituted, solution should be stored refrigerated at 2–8°C and used within the timeframe indicated on the product's documentation, avoiding repeated freeze-thaw cycles. Researchers should note that the specialized heat-stable pharmaceutical formulation used in global health applications and large trials like CHAMPION involves proprietary formulation technology beyond standard lyophilized peptide handling, and standard research-grade Carbetocin should not be assumed to share the same room-temperature stability profile without proper formulation.
Frequently asked questions about Carbetocin
What is Carbetocin and how does it differ from Oxytocin?
Carbetocin is a synthetic, long-acting analog of oxytocin, modified with a 1-deamino change, O-methylation at position 2, and a stable thioether cyclization in place of oxytocin's native disulfide bond. These modifications extend its half-life from oxytocin's roughly 3.4 minutes to approximately 85-100 minutes.
Is Carbetocin FDA approved?
No. It has been approved for decades in the European Union (as Pabal), Canada (as Duratocin), and many other countries for preventing postpartum hemorrhage, but has not received FDA approval for use in the United States.
What is the WHO CHAMPION trial and why is it significant?
A large international trial (Widmer et al. 2018, PMID 29949473) across 23 hospitals in 10 countries found heat-stable carbetocin noninferior to oxytocin for preventing postpartum hemorrhage after vaginal birth. Its significance lies in heat-stable carbetocin not requiring the cold-chain refrigeration oxytocin needs, addressing a major real-world barrier to hemorrhage prevention in lower-resource settings.
What is the mechanism of action of Carbetocin?
Carbetocin activates oxytocin receptors on uterine smooth muscle, triggering sustained uterine contraction that helps limit postpartum blood loss by compressing blood vessels at the placental attachment site.
What evidence supports Carbetocin's use after cesarean section specifically?
Attilakos et al. (2010, PMID 20482535), a UK double-blind RCT, found significantly fewer women needed additional uterotonic medications with carbetocin versus oxytocin (33.5% versus 45.5%) after cesarean delivery, though no significant difference was found in severe hemorrhage rates.
Why does postpartum hemorrhage prevention matter globally?
Postpartum hemorrhage is the leading cause of maternal death worldwide. Standard oxytocin requires cold-chain refrigeration unavailable in many regions, which is why the WHO has specifically recommended heat-stable carbetocin as an option where maintaining an oxytocin cold chain is not feasible.
What administration routes have been used in Carbetocin's pivotal trials?
Intravenous and intramuscular administration in clinical trials. This describes methodology used in published clinical research, not usage instructions — Verified Peptides does not provide dosing guidance for human or animal administration.
Does Carbetocin have the same social-bonding research relevance as Oxytocin?
Not to the same extent. Carbetocin has been developed and studied almost exclusively for its peripheral uterotonic effect, with a much more limited independent research literature addressing central nervous system or social-behavioral dimensions of oxytocin receptor activity compared to native Oxytocin.
Legal & research status: Carbetocin is approved in the European Union (as Pabal), Canada (as Duratocin), and numerous other countries for preventing postpartum hemorrhage, but has not received FDA approval for use in the United States. Material sold as a research compound is offered strictly for laboratory and research use, not for human consumption or therapeutic use.