Atosiban Acetate is an inhibitor of the hormones oxytocin and vasopressin. It is used intravenously to halt premature labor.
Atosiban is a synthetic peptide oxytocin antagonist. It binds to membrane bound oxytocin receptors on the myometrium and prevents oxytocin-stimulated increases in inositol triphosphate production. This prevents release of stored calcium from the sarcoplasmic reticulum and subsequent opening of voltage gated calcium channels. This shutdown of cytosolic calcium increase prevents contractions of the uterine muscle, reducing the frequency of contractions and inducing uterine quiescence.