Hyponatremia or hyponatraemia is a low concentration of sodium in the blood. It is generally defined as a sodium concentration of less than 135 mmol/L (135 mEq/L), with severe hyponatremia being below 120 mEq/L. Symptoms can be absent, mild or severe. Mild symptoms include a decreased ability to think, headaches, nausea, and poor balance. Severe symptoms include confusion, seizures, and coma; death can ensue.
Human vasopressin, also called antidiuretic hormone (ADH), arginine vasopressin (AVP) or argipressin, is a hormone synthesized from the AVP gene as a peptide prohormone in neurons in the hypothalamus, and is converted to AVP. It then travels down the axon terminating in the posterior pituitary, and is released from vesicles into the circulation in response to extracellular fluid hypertonicity (hyperosmolality). AVP has two primary functions. First, it increases the amount of solute-free water reabsorbed back into the circulation from the filtrate in the kidney tubules of the nephrons. Second, AVP constricts arterioles, which increases peripheral vascular resistance and raises arterial blood pressure.
Desmopressin, sold under the trade name DDAVP among others, is a medication used to treat diabetes insipidus, bedwetting, hemophilia A, von Willebrand disease, and high blood urea levels. In hemophilia A and von Willebrand disease, it should only be used for mild to moderate cases. It may be given in the nose, by injection into a vein, by mouth, or under the tongue.
Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is characterized by excessive unsuppressible release of antidiuretic hormone (ADH) either from the posterior pituitary gland, or an abnormal non-pituitary source. Unsuppressed ADH causes an unrelenting increase in solute-free water being returned by the tubules of the kidney to the venous circulation.
Conivaptan, sold under the brand name Vaprisol, is a non-peptide inhibitor of the receptor for anti-diuretic hormone, also called vasopressin. It was approved in 2004 for hyponatremia. The compound was discovered by Astellas and marked in 2006. The drug is now marketed by Cumberland Pharmaceuticals, Inc.
Demeclocycline is a tetracycline antibiotic which was derived from a mutant strain of Streptomyces aureofaciens.
Vasopressin receptor 1A (V1AR), or arginine vasopressin receptor 1A is one of the three major receptor types for vasopressin, and is present throughout the brain, as well as in the periphery in the liver, kidney, and vasculature.
Vasopressin V1b receptor (V1BR) also known as vasopressin 3 receptor (VPR3) or antidiuretic hormone receptor 1B is a protein that in humans is encoded by the AVPR1B gene.
Vasopressin receptor 2 (V2R), or arginine vasopressin receptor 2, is a protein that acts as receptor for vasopressin. AVPR2 belongs to the subfamily of G-protein-coupled receptors. Its activity is mediated by the Gs type of G proteins, which stimulate adenylate cyclase.
The actions of vasopressin are mediated by stimulation of tissue-specific G protein-coupled receptors (GPCRs) called vasopressin receptors that are classified into the V1 (V1A), V2, and V3 (V1B) receptor subtypes. These three subtypes differ in localization, function and signal transduction mechanisms.
Tolvaptan, sold under the brand name Samsca among others, is an aquaretic drug that functions as a selective, competitive vasopressin receptor 2 (V2) antagonist used to treat hyponatremia (low blood sodium levels) associated with congestive heart failure, cirrhosis, and the syndrome of inappropriate antidiuretic hormone (SIADH). Tolvaptan was approved by the U.S. Food and Drug Administration (FDA) on May 19, 2009, and is sold by Otsuka Pharmaceutical Co. under the trade name Samsca. Tolvaptan, as Jynarque, was granted approval for medical use in the United States in April 2018.
Nelivaptan (INN) is a selective, orally active, non-peptide vasopressin receptor antagonist selective for the V1B subtype. The drug had entered clinical trials for treatment of anxiety and depression. In July 2008, Sanofi-Aventis announced that further development of this drug had been halted.
A vasopressin receptor antagonist (VRA) is an agent that interferes with action at the vasopressin receptors. Most commonly VRAs are used in the treatment of hyponatremia, especially in patients with congestive heart failure, liver cirrhosis or SIADH.
Relcovaptan (SR-49059) is a non-peptide vasopressin receptor antagonist, selective for the V1a subtype. It has shown positive initial results for the treatment of Raynaud's disease and dysmenorrhoea, and as a tocolytic, although it is not yet approved for clinical use.
Lixivaptan (VPA-985) is an orally-active, non-peptide, selective vasopressin 2 receptor antagonist being developed as an investigational drug by Palladio Biosciences, Inc. (Palladio), a subsidiary of Centessa Pharmaceuticals plc. As of December 2021, lixivaptan is in Phase III clinical development for the treatment of Autosomal dominant polycystic kidney disease (ADPKD), the most common form of polycystic kidney disease. The U.S. Food and Drug Administration (FDA) has granted orphan drug designation to lixivaptan for the treatment of ADPKD.
A fluid restriction diet is a diet which limits the amount of daily fluid consumption. Besides beverages, many foods also include fluids which needs to be taken into consideration. A fluid-restrictive diet assists in preventing the build-up of fluids in the body. Reducing fluid intake can alleviate stress on the body and may reduce additional complications. A fluid restriction diet is generally medically advised for patients with "heart problems, renal disease, liver damage including cirrhosis, endocrine and adrenal gland issues, elevated stress hormones and hyponatremia". Patients with heart failure are recommended to restrict fluid intake down to 2 quarts per day.
PF-184563 is a potent, selective non-peptidic antagonist of the V1a receptor. The compound was discovered by Pfizer in its Sandwich, Kent research center, as a potential treatment for dysmenorrhoea, an indication for which V1a antagonists have shown efficacy.
Epelsiban is an orally bioavailable drug which acts as a selective and potent oxytocin receptor antagonist. It was initially developed by GlaxoSmithKline (GSK) for the treatment of premature ejaculation in men and then as an agent to enhance embryo or blastocyst implantation in women undergoing embryo or blastocyst transfer associated with in vitro fertilization (IVF)., and was also investigated for use in the treatment of adenomyosis.
Merotocin (INN) (developmental code name FE-202767), also known as carba-1-(4-FBzlGly7)dOT, is a peptidic agonist of the oxytocin receptor that was derived from oxytocin. It is under development by Ferring Pharmaceuticals for the treatment of preterm mothers with lactation failure requiring lactation support, and is in phase II clinical trials for this indication. Merotocin is potent (EC50 < 0.1 nM) and highly selective (>1000-fold over the related vasopressin receptors).
Vasopressin infusions are in use for septic shock patients not responding to fluid resuscitation or infusions of catecholamines to increase the blood pressure while sparing the use of catecholamines. These argipressins have much shorter elimination half-life than synthetic non-arginine vasopresines with much longer elimination half-life of many hours. Further, argipressins act on V1a, V1b, and V2 receptors which consequently lead to higher eGFR and lower vascular resistance in the lungs. A number of injectable arginine vasopressins are in clinical use in the United States and the European Union. Pitressin among others, is a medication most commonly used in the treatment of frequent urination, increased thirst, and dehydration such as that resulting from diabetes insipidus, which causes increased and diluted urine. It is used to treat abdominal distension following some surgeries, and in stomach roentgenography. Vasopressin is a hormone that affects the kidneys and reduces urine flow.
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