Tolvaptan: a vasopressin antagonist for the management of euvolemic and hypervolemic hyponatremia.

Tolvaptan is a new vasopressin antagonist developed for the treatment of hypervolemic or euvolemic hyponatremia. It has greater affinity for the V(2) receptor than native vasopressin or any other vasopressin antagonist. Blockade of the V(2) receptor induces solute-free water excretion without affecting normal electrolyte excretion. The pharmacokinetics and pharmacodynamics of tolvaptan are suitable for once-daily dosing. Throughout all phases of clinical studies, it was shown to be safe for short- and long-term use. Tolvaptan effectively increases serum sodium levels in patients with heart failure, cirrhosis and syndrome of inappropriate secretion of antidiuretic hormone. In patients hospitalized owing to heart failure, tolvaptan decreased bodyweight, increased urine output and improved dyspnea compared with placebo. However, tolvaptan has not proven to be beneficial for the long-term management of heart failure. Currently, tolvaptan is the only oral agent in its class available in the USA and Europe.