OPC-21268, a non-peptide vasopressin V1 receptor antagonist, inhibited oxytocin- and vasopressin-induced contractions of myometrial strips from rats and from full-term pregnant women. OPC-21268, because of its non-peptide structure, is orally active and has been shown to lower blood pressure in a patient with congestive heart failure and in spontaneously hypertensive rats. It also attenuates vasopressin induced bradycardia in rabbits and pressor responses in rats. It has been demonstrated that OPC-21268 exerts its inhibitory action through binding to the vasopressin V1 receptors in rat liver and kidney. Finally, OPC-21268 was reported to be safe and non-toxic in healthy humans. Merck scientists showed that OPC-21268 had significant affinity for the rOTR and the hOTR. OPC-21268 has been in phase II clinical trials by Otsuka for the treatment of heart failure and hypertension. However, this research has been discontinued.

Mozavaptan hydrochloride was approved by Pharmaceuticals and Medical Devices Agency of Japan (PMDA) on July 26, 2006. It was developed and marketed as Physuline® by Otsuka in Japan. Mozavaptan hydrochloride is a vasopressin receptor antagonist. It is indicated for the treatment of hyponatremia due to excessive fluid retention when restriction of fluid intake is ineffective. Physuline® is available as film-coated tablet for oral use, containing 30 mg of Mozavaptan hydrochloride. The recommended dose is one tablet (30 mg) once daily after a meal.

More than a century ago, Sir Henry Dale demonstrated that a component of the pituitary causes contractions of the mammalian uterus, hence his coining the term “oxytocic,” derived from the Greek for “quick birth,” for its activity. The discovery that a component of the pituitary causes milk secretion followed within a few years. By 1930, oxytocin was separated from vasopressin into pitocin and pitressin, respectively, at Parke Davis and made available for research. That a single peptide was responsible for these uterine and mammary actions was definitively confirmed upon the sequencing and synthesis of the peptide, 9 amino acids in length. Vincent du Vigneaud was awarded a Nobel Prize for this work. Oxytocin is indicated for the initiation or improvement of uterine contractions, where this is desirable and considered suitable for reasons of fetal or maternal concern, in order to achieve vaginal delivery. Oxytocin is indicated to produce uterine contractions during the third stage of labor and to control postpartum bleeding or hemorrhage. Uterine motility depends on the formation of the contractile protein actomyosin under the influence of the Ca2+- dependent phosphorylating enzyme myosin light-chain kinase. Oxytocin promotes contractions by increasing the intracellular Ca2+. Oxytocin has specific receptors in the myometrium and the receptor concentration increases greatly during pregnancy, reaching a maximum in early labor at term. The Oxytocin receptor is a typical class I G protein-coupled receptor that is primarily coupled via G(q) proteins to phospholipase C-beta. The high-affinity receptor state requires both Mg(2+) and cholesterol, which probably function as allosteric modulators. The agonist-binding region of the receptor has been characterized by mutagenesis and molecular modeling and is different from the antagonist binding site. The function and physiological regulation of the Oxytocin system is strongly steroid dependent.

Argipressin is a neurohypophysial hormone from the vasopressin hormone family. Its two primary functions are to retain water in the body and to constrict blood vessels. The antidiuretic action of Argipressin is ascribed to increase in reabsorption of water by the renal tubules. Argipressin can cause contraction of smooth muscle of the gastrointestinal tract, gall bladder, urinary bladder and all parts of the vascular bed, especially the capillaries, small arterioles and venules with less effect on the smooth musculature of the large veins. Agripressin for injections is used for use in diabetes insipidus, when this is not of nephrogenic origin and control of bleeding from oesophageal varices. In addition, argipressin is indicated to increase blood pressure in adults with vasodilatory shock (e.g., post-cardiotomy or sepsis) who remain hypotensive despite fluids and catecholamines.