<qa>  What is the non-osmotic secretion of arginine vasA common theme underlying the occurrence of hyponatremia whether in the setting of congestive heart failure, hepatic failure with ascites, or the syndrome of inappropriate anti-diuretic hormone SIADH is the non-osmotic secretion of arginine vasopressin AVP. The presence of excess AVP leads to fluid retention and hyponatremia. Agents that antagonize AVP, causing proportionally more water diuresis than solute excretion, could offer a significant treatment option for patients with hyponatremia, compared to fluid restriction alone. Treatment of hyponatremia, particularly in clinical settings such as decompensated congestive heart failure, is difficult as conventional diuretics cause neurohormonal activation and further stimulate the inappropriate release of vasopressin, leading to additional retention of free water and aggravation of hypoosmolality. Similarly, for cirrhosis with ascites and SIADH, conventional diuretics are either minimally effective or completely contraindicated. An alternative approach to symptom relief and treatment of hyponatremia may be the use of vasopressin antagonists, which increase free water clearance with proportionally less effect on sodium excretion. Tolvaptan is an oral vasopressin antagonist with relative affinity for the V2 receptor which has been shown to induce a diuresis with proportionally more free-water than sodium loss. 