Effects of the non-peptide inhibitor OPC-21268 on oxytocin and vasopressin stimulation of rat and human myometrium.

OPC-21268 (1-[-1-[4-(3-acetylaminopropoxy)benzoyl]-piperidyl]-3,4- dihydro-2(1H)-quinolinone), a non-peptide vasopressin V1 receptor antagonist, inhibited oxytocin- and vasopressin-induced contractions of myometrial strips from rats and from full-term pregnant women. Administered intravenously in rats the drug also inhibited uterine contractions caused by infusion of oxytocin. When incubated with purified plasma membranes from rat or human myometrial tissue, OPC-21268 inhibited the specific receptor binding of tritiated oxytocin and vasopressin in a dose-dependent and reversible way.