Evaluation of 1-Deamino-[D-Tyr(Oethyl)2, Thr4, Orn8] Vasotocin, an Oxytocin Antagonist in Animal Models of Uterine Contractility and Preterm...

Evaluation of 1-deamino-[D-Tyr(Oethyl)2, Thr4, Orn8] vasotocin, an oxytocin antagonist in animal models of uterine contractility and preterm labor: A new tocolytic agent

Abstract

We attempted to characterize the ability of a new oxytocin derivative, 1-deamino[D-Tyr(Oethyl)2,Thr4,Orn8] vasotocin (ORF 22164), to antagonize the action of oxytocin in several in vitro and in vivo animal models of uterine hyperactivity. In these studies, the derivative was found to be a specific competitive inhibitor of oxytocin-induced contractions of pregnant guinea pig uterus in vitro. In addition, its intravenous administration induced a dose-dependent inhibition of oxytocin-induced uterine contractions in situ. Finally, like ritodrine, the drug induced a dose-dependent delay of ongoing labor in rats. These results suggest that 1-deamino-[D-Tyr(Oethyl)2,Thr4,Orn8] vasotocin, unlike ritodrine, is a potent and specific antagonist of oxytocin-induced uterine contractions and thus may have potential clinical utility in the treatment of preterm labor.