Epelsiban (GSK557296), a pyridyl-2,5-diketopiperazine, is a potent, highly selective, and orally bioavailable non-peptide oxytocin receptor antagonist. GlaxoSmithKline was developing epelsiban for the treatment of women infertility due to adenomyosis and premature ejaculation.

Atosiban (brand name Tractocile) is a competitive antagonist of human oxytocin at receptor level. In rats and guinea pigs, atosiban was shown to bind to oxytocin receptors, to decrease the frequency of contractions and the tone of the uterine musculature, resulting in a suppression of uterine contractions. Atosiban was also shown to bind to the vasopressin receptor, thus inhibiting the effect of vasopressin. Tractocile is indicated to delay imminent pre-term birth in pregnant adult women with: − regular uterine contractions of at least 30 seconds duration at a rate of ≥ 4 per 30 minutes − a cervical dilation of 1 to 3 cm (0-3 for nulliparas) and effacement of ≥ 50% − a gestational age from 24 until 33 completed weeks − a normal foetal heart rate. Atosiban does not have U.S. Food and Drug Administration (FDA) approval for use in the United States.