Oral tolvaptan is safe and effective in chronic hyponatremia.

Vasopressin antagonists increase the serum sodium concentration in patients who have euvolemia and hypervolemia with hyponatremia in the short term (145 mmol/L) led to discontinuation in one patient. Mean serum sodium increased from 130.8 mmol/L at baseline to >135 mmol/L throughout the observation period (P < 0.001 versus baseline at most points). Responses were comparable between patients with euvolemia and those with heart failure but more modest in patients with cirrhosis. In conclusion, prolonged administration of tolvaptan maintains an increased serum sodium with an acceptable margin of safety.