Peptide LibraryAtosiban
Atosiban is an oxytocin receptor antagonist. Atosiban is a modified oxytocin analog that competitively antagonises the oxytocin receptor on uterine myometrium and decidua, reducing oxytocin-driven intracellular calcium release and prostaglandin production and thereby suppressing uterine contractions. Its receptor selectivity gives it a narrower systemic side-effect profile than non-selective tocolytics such as beta agonists.
For research use only.
Key Facts
- CAS
- 90779-69-4
- Molecular Weight (MW)
- 994.2 g/mol
- Half-life
- Initial half-life about 0.21 hours and terminal half-life about 1.7 hours in women in preterm labour
- FDA status
- Not Approved
- Evidence level
- Established Human Evidence
- Human dose established
- Yes
- Administration Route
- Intravenous
- Frequency
- Bolus followed by continuous infusion
- Last updated
- Nov 7, 2026
- Reviewed
- Nov 7, 2026
Research summary
Oxytocin receptor antagonist used in Europe and elsewhere as a tocolytic to delay imminent preterm birth. It is not approved by the FDA in the United States.
Research evidence
- Regulatory review (FDA label)None in reviewed sources
- Controlled human trials3 reviewed sources
- Early or uncontrolled human studiesOnly in 1 review or summary
- Lab & animal studiesNone in reviewed sources
How it works
Each step shows whether the sources Peptide Library has reviewed include that kind of research. Counts are reviewed sources, not every study ever published. Reviews and programme summaries that describe human use are shown as "reported", not as trials, and registered trials without published results are listed but not counted. A higher step means research has progressed further; it does not mean a compound works better or is safer. Compounds whose evidence has not been reviewed yet show "Not reviewed" instead of a guess.
Peptide Library's Atosiban profile summarises 5 cited studies listed in the Science section, the compound's regulatory status, and research-protocol parameters reported for it. It is a research reference, not medical advice.
Atosiban dosage evidence
Atosiban has no FDA-approved dosage, but it is authorised in the European Union as Tractocile to delay imminent preterm birth at 24 to 33 completed weeks. The EU product information gives three intravenous steps: a 6.75 mg bolus over one minute, an infusion of 300 mcg a minute for 3 hours, then 100 mcg a minute for up to 45 hours, with treatment not exceeding 48 hours. The APOSTEL 8 trial found no improvement in newborn outcomes over placebo at 30 to 34 weeks.
| Human dosing established | Yes |
|---|---|
| Route | Intravenous |
| Frequency | Bolus followed by continuous infusion |
| Duration studied | No more than 48 hours per course |
| Titration | Bolus 6.75 mg over 1 minute; loading infusion 300 mcg/minute (24 mL/hour) for 3 hours (54 mg); then 100 mcg/minute (8 mL/hour) for up to 45 hours (up to 270 mg). The EU product information says a full course should preferably not exceed 330.75 mg. |
| Half-life | Initial half-life about 0.21 hours and terminal half-life about 1.7 hours in women in preterm labour |
| Evidence level | Established Human Evidence |
| Last reviewed | 2026-11-07 |
Research-reported dosing
Doses as studied, one row per regimen. Different trials used different regimens; they are listed separately rather than averaged.
| Study / context | Population | Dose | Route | Frequency | Duration | Outcome studied | Source |
|---|---|---|---|---|---|---|---|
| EU product information — Tractocile, imminent preterm birth (EMA)Research-reported · EU regulatory product information (summary of product characteristics) | Pregnant adult women at 24 to 33 completed weeks with regular contractions, cervical dilation of 1–3 cm (0–3 cm in nulliparas), effacement of at least 50% and a normal fetal heart rate | 6.75 mg bolus, then 300 mcg/minute for 3 hours, then 100 mcg/minute for up to 45 hours | Intravenous | Bolus, then continuous infusion | Up to 48 hours; up to 3 re-treatments have limited clinical experience | Authorised in the EU to delay imminent preterm birth | Tractocile (atosiban) 6.75 mg/0.9 mL solution for injection — EU summary of product characteristics, EMA |
| Atosiban versus placebo in late threatened preterm birth — registry record (NCT05693688)Clinical trial · Randomised, double-blind, placebo-controlled phase 4 trial | Women 18 or older with a singleton or twin pregnancy and threatened preterm birth at 30+0 to 33+6 weeks (760 enrolled) | 6.75 mg bolus over one minute, then 18 mg/hour for 3 hours, then 6 mg/hour for the remaining 45 hours, or saline placebo | Intravenous | Bolus, then continuous infusion | 48 hours | Completed; no results are posted on ClinicalTrials.gov | NCT05693688 — Atosiban Versus Placebo in the Treatment of Late Threatened Pre-term Birth |
| APOSTEL 8 — Lancet 2025Clinical trial · Multicentre, randomised, double-blind superiority trial | Women aged 18 or older with a singleton or twin pregnancy and threatened preterm birth at 30+0 to 33+6 weeks (752 analysed) | Intravenous atosiban or placebo (regimen not stated in the indexed abstract) | Intravenous | Not stated in the indexed abstract | Not stated in the indexed abstract | Primary composite of perinatal death and severe newborn illness: 8% of infants with atosiban versus 9% with placebo (RR 0.90, 95% CI 0.58–1.40); superiority not shown | Atosiban versus placebo for threatened preterm birth (APOSTEL 8): a multicentre, randomised controlled trial. Lancet. 2025. |
| US placebo-controlled trial with tocolytic rescue (2000)Clinical trial · Multicentre, double-blind, placebo-controlled trial | Women in preterm labour (501 treated: 246 atosiban, 255 placebo) | Intravenous atosiban, then subcutaneous maintenance (amounts not stated in the indexed abstract) | Intravenous, then subcutaneous | Not stated in the indexed abstract | Not stated in the indexed abstract | No difference in time to delivery or treatment failure (primary endpoint; median 25.6 versus 21.0 days); more women stayed undelivered without another tocolytic at 24 hours, 48 hours and 7 days; fetal-infant deaths were higher with atosiban among those randomised before 24 weeks | An oxytocin receptor antagonist (atosiban) in the treatment of preterm labor: a randomized, double-blind, placebo-controlled trial with tocolytic rescue. Am J Obstet Gynecol. 2000. |
Where sources disagree
- Atosiban is an oxytocin receptor antagonist; the EU product information says treatment should be started and maintained by a physician experienced in treating preterm labour. The EU product information contraindicates it below 24 or after 33 completed weeks, with ruptured membranes after 30 weeks, abnormal fetal heart rate, bleeding needing immediate delivery, severe pre-eclampsia or eclampsia, fetal death, suspected infection, placenta praevia or abruption, and any other condition where continuing the pregnancy is hazardous.
- The FDA has not approved atosiban, and there is no atosiban label on DailyMed. The EU dosing row is marked as a regulatory document rather than a trial because the schema has no category for a non-US approval.
Sequence & molecular data
| Molecular formula | C43H67N11O12S2 |
|---|---|
| Molecular weight | 994.2 g/mol |
| CAS number | 90779-69-4 |
| PubChem CID | 5311010 |
| FDA UNII | 081D12SI0Z |
| ChEMBL | CHEMBL382301 |
| DrugBank | DB09059 |
Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.
Science
Mechanism of Action
Atosiban is a modified oxytocin analog that competitively antagonises the oxytocin receptor on uterine myometrium and decidua, reducing oxytocin-driven intracellular calcium release and prostaglandin production and thereby suppressing uterine contractions. Its receptor selectivity gives it a narrower systemic side-effect profile than non-selective tocolytics such as beta agonists.
Studies
- Efficacy of atosiban for repeated embryo implantation failure: A systematic review and meta-analysis
- Randomised, triple-blind, placebo-controlled trial of atosiban in women with previous embryo implantation failure and abnormal uterine contractions undergoing single blastocyst-stage embryo transfer: a study protocol
- Atosiban versus placebo for threatened preterm birth (APOSTEL 8): a multicentre, randomised controlled trial
- Interventions to optimize embryo transfer in women undergoing assisted conception: a comprehensive systematic review and meta-analyses
- The safety of tocolytics used for the inhibition of preterm labour
Research statistics
545 PubMed publications · 29.4% human clinical research · 22 registered trials
Counts of published research through 2026-11-01, not evidence that it works. Publications by year, study types and trials · How publications are counted
Regulatory & research status
Atosiban is not an FDA-approved product. It is sold for laboratory research and has no approved medical use.
| FDA status | Not Approved |
|---|---|
| Research status | Research-only compound; no approval pathway listed |
| Availability | Prescription-Only |
| WADA (sport) | Unknown / Not Listed |
| Library classification | Clinical Trial |
How FDA approval, compounding and research-only status differ
Benefits
—
Atosiban side effects
No side effects listed yet for this entry.
Storage & stability
This compound is not supplied as a powder to be mixed, so the freeze-dried powder and reconstitution handling described for research peptides does not apply. Storage conditions are product-specific: follow the label or packaging of the product itself.
Atosiban: frequently asked questions
What is Atosiban?
Oxytocin receptor antagonist used in Europe and elsewhere as a tocolytic to delay imminent preterm birth. It is not approved by the FDA in the United States.
How does Atosiban work?
Atosiban is a modified oxytocin analog that competitively antagonises the oxytocin receptor on uterine myometrium and decidua, reducing oxytocin-driven intracellular calcium release and prostaglandin production and thereby suppressing uterine contractions. Its receptor selectivity gives it a narrower systemic side-effect profile than non-selective tocolytics such as beta agonists.
Is Atosiban FDA approved?
No. Atosiban is not approved by the FDA for any indication and is categorised as prescription-only. It has not been reviewed for safety or efficacy as a medicine, and published research should be read as investigation rather than established use.
What peptides are similar to Atosiban?
Compounds most often compared with Atosiban include Oxytocin, Carbetocin, ARA 290 (Cibinetide) and Serelaxin. They are grouped by shared mechanism or research area rather than by equivalence, and their regulatory status and evidence base differ.
References
- Efficacy of atosiban for repeated embryo implantation failure: A systematic review and meta-analysis — Front Endocrinol (Lausanne), 2023External reference
- Randomised, triple-blind, placebo-controlled trial of atosiban in women with previous embryo implantation failure and abnormal uterine contractions undergoing single blastocyst-stage embryo transfer: a study protocol — BMJ Open, 2026External reference
- Atosiban versus placebo for threatened preterm birth (APOSTEL 8): a multicentre, randomised controlled trial — Lancet, 2025External reference
- Interventions to optimize embryo transfer in women undergoing assisted conception: a comprehensive systematic review and meta-analyses — Hum Reprod Update, 2022External reference
- The safety of tocolytics used for the inhibition of preterm labour — Expert Opin Drug Saf, 2016External reference
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Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Nov 7, 2026 · Version 2
This Atosiban profile is compiled from published literature (5 cited studies linked above), public regulatory records and chemical registries. It describes what research reports; it is not medical advice, and nothing here is a dosing recommendation for humans. Peptide Library does not sell peptides. Editorial policy · How profiles are compiled · Report an error
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