--- title: "Atosiban" canonical_url: https://peptidelibrary.app/library/atosiban description: "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." updated: 2026-11-07 publisher: Peptide Library notice: "Research and educational use only. Not medical advice." --- # Atosiban 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. 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. ## Classification - Type: Oxytocin receptor antagonist - Mechanism class: Oxytocin Receptor Antagonist - Development stage: Research only - Regulatory class: Investigational, not FDA-approved ## Mechanism 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. ## Properties - Molecular formula: C43H67N11O12S2 - Molecular weight: 994.2 g/mol - CAS number: 90779-69-4 - Half-life: Initial half-life about 0.21 hours and terminal half-life about 1.7 hours in women in preterm labour - Studied routes: Intravenous ## Evidence - Evidence level: Established Human Evidence - Highest documented: Controlled human trials - Human trials: 3 - Controlled human trials: 3 - Preclinical sources: 0 - Latest source: 2025 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. ### Studies 1. Cited source (title omitted: it states a dose). Secondary report (review or programme summary), not a trial. Population: 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. Authorised in the EU to delay imminent preterm birth. Limitations: Reported in research, not a controlled trial. [Source](https://www.ema.europa.eu/en/documents/product-information/tractocile-epar-product-information_en.pdf) 2. NCT05693688 — Atosiban Versus Placebo in the Treatment of Late Threatened Pre-term Birth. Controlled human trial. Population: Women 18 or older with a singleton or twin pregnancy and threatened preterm birth at 30+0 to 33+6 weeks (760 enrolled). Completed; no results are posted on ClinicalTrials.gov [Source](https://clinicaltrials.gov/study/NCT05693688) 3. Atosiban versus placebo for threatened preterm birth (APOSTEL 8): a multicentre, randomised controlled trial. Lancet. 2025. 2025. Controlled human trial. Population: Women aged 18 or older with a singleton or twin pregnancy and threatened preterm birth at 30+0 to 33+6 weeks (752 analysed). 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 [Source](https://pubmed.ncbi.nlm.nih.gov/40049187/) 4. 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. 2000. Controlled human trial. Population: Women in preterm labour (501 treated: 246 atosiban, 255 placebo). 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 [Source](https://pubmed.ncbi.nlm.nih.gov/10819855/) ### Registered trials - [NCT05693688](https://clinicaltrials.gov/study/NCT05693688) ## Safety Human safety basis: Clinical trial reports Key limitations: Not approved by the FDA for any use.. ## Regulatory status Atosiban is not an FDA-approved product. It is sold for laboratory research and has no approved medical use. - FDA status: Not Approved - Availability: Prescription-Only ## 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), 2023](https://pubmed.ncbi.nlm.nih.gov/37033236/) - [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, 2026](https://pubmed.ncbi.nlm.nih.gov/42229962/) - [Atosiban versus placebo for threatened preterm birth (APOSTEL 8): a multicentre, randomised controlled trial — Lancet, 2025](https://pubmed.ncbi.nlm.nih.gov/40049187/) - [Interventions to optimize embryo transfer in women undergoing assisted conception: a comprehensive systematic review and meta-analyses — Hum Reprod Update, 2022](https://pubmed.ncbi.nlm.nih.gov/35325124/) - [The safety of tocolytics used for the inhibition of preterm labour — Expert Opin Drug Saf, 2016](https://pubmed.ncbi.nlm.nih.gov/27159501/) Note: Dose figures are left out of this Markdown version. See the cited sources.