Atosiban Acetate is indicated for delaying imminent preterm birth in pregnant adult women who meet the following criteria:

• Regular uterine contractions lasting at least 30 seconds, occurring ≥4 times within 30 minutes
• Cervical dilation of 1–3 cm (0–3 cm in nulliparous women) with ≥50% effacement
• Gestational age between 24 and 33 completed weeks
• Normal fetal heart rate

Atosiban binds to oxytocin receptors located on the uterine myometrium and blocks oxytocin-induced signaling. It inhibits the production of inositol triphosphate, preventing the release of intracellular calcium from the sarcoplasmic reticulum and reducing calcium influx through voltage-gated channels. By lowering intracellular calcium levels, atosiban suppresses uterine muscle contractions, decreases contraction frequency, and promotes uterine relaxation.

Additionally, atosiban acts as a biased ligand at oxytocin receptors. It inhibits Gq-mediated signaling pathways responsible for uterine contraction, while activating Gi pathways, which may induce pro-inflammatory effects via NF-κB activation. This inflammatory response may partially reduce its effectiveness compared to other tocolytic agents.

Atosiban is administered intravenously in three successive stages: an initial bolus dose (6.75 mg), performed with Atosiban 6.75 mg/0.9 ml solution for injection, immediately followed by a continuous high dose infusion (loading infusion 300 micrograms/min) of Atosiban 37.5 mg/5 ml concentrate for solution for infusion during three hours, followed by a lower dose of Atosiban 37.5 mg/5 ml concentrate for solution for infusion (subsequent infusion 100 micrograms/min) up to 45 hours. The duration of the treatment should not exceed 48 hours. The total dose given during a full course of Atosiban therapy should preferably not exceed 330.75 mg of atosiban.

Atosiban Acetate is unlikely to be involved in cytochrome P450–mediated drug interactions, as it is neither a substrate nor an inhibitor of these enzymes.

Clinical studies with labetalol and betamethasone in healthy female volunteers have shown no clinically significant interactions.

Atosiban is contraindicated in the following conditions:

• Gestational age less than 24 weeks or more than 33 completed weeks
• Premature rupture of membranes beyond 30 weeks of gestation
• Abnormal fetal heart rate
• Antepartum uterine bleeding requiring immediate delivery
• Eclampsia or severe pre-eclampsia requiring delivery
• Intrauterine fetal death
• Suspected intrauterine infection
• Placenta previa
• Placental abruption
• Any maternal or fetal condition where continuation of pregnancy is unsafe

Very common: Nausea.

Common: Headache, dizziness, flushing, vomiting, tachycardia, hypotension (with symptoms like dizziness or light-headedness), injection site reactions, and elevated blood glucose.

Uncommon: Fever, insomnia, itching, and rash.

If a patient is pregnant and breastfeeding an older child, breastfeeding should be discontinued during treatment with atosiban.

• In cases where premature rupture of membranes is suspected, the benefits of delaying delivery should be weighed against the risk of chorioamnionitis
• Use cautiously in patients with hepatic impairment; limited data are available
• No dose adjustment is usually required in renal impairment
• Limited clinical experience exists in multiple pregnancies and gestational age 24–27 weeks
• Re-treatment is possible, but data on repeated courses (up to 3) are limited
• In intrauterine growth restriction, continuation depends on fetal maturity assessment
• Monitor uterine contractions and fetal heart rate during treatment
• May increase the risk of postpartum bleeding; monitor blood loss
• Use cautiously in multiple pregnancy or when combined with other tocolytic agents due to risk of pulmonary edema

Tocolytic agent.

Store in a refrigerator at 2°C–8°C, protected from light and moisture. Keep out of reach of children.