Vasopressin antagonists in treatment of hyponatremia

Hyponatremia is the most frequently encountered electrolyte disturbance in hospitalized patients. It is usually caused by dysregulation of arginine vasopressin (AVP) homeostasis which accompanies disorders associated with water retention such as congestive heart failure and cirrhosis, or follows euvolemic states such as syndrome of inapprioprate secretion of antidiuretic hormone. Available therapy, i.e. restriction of fluid intake, saline and diuretics, is often ineffective with unpredictable results and potentially serious side effects. Recent clinical trials with non-peptide AVP receptor antagonists (vaptans) have indicated that these drugs are effective in the treatment of hyponatremia. Vaptans lead to aquaresis, an electrolyte-sparing excretion of free water, that results in the correction of serum sodium concentration. Until now the Food and Drug Administration in the USA has approved the use of intravenous conivaptan for treatment of euvolemic hyponatremia. In this article, we review results from recent clinical trials on vaptans (lixivaptan, tolvaptan, conivaptan and satavaptan) which showed their efficacy in the treatment of hyponatremia.