Atosiban also called ADH (Anti-Diuretic Hormone) has a molecular formula of C43H67N11O12S2, Mpr-Tyr(OEt)-Ile-Thr-Asn-Cys-Pro-Orn-Gly-NH2 having a Mw of 994.2 is the first oxytocin antagonist to be specifically developed for the treatment of preterm labour. Atosiban has a specific mode of action, inhibiting oxytocin-induced uterine contractions lry blocking oxytocin receptors in the uterus. Extensive clinical investigations have shown Atosiban to be at least as effective as current tocolytic agents. In addition, due to its novel and specific mode of action, Atosiban has a markedly improved maternal side effects profile compared with conventional therapies.