Tolvaptan

Tolvaptan is an orally administered, nonpeptide, selective arginine vasopressin V(2) receptor antagonist that increases free water clearance, thereby correcting low serum sodium levels. SALT-1 and -2, two identical, randomized, double-blind, placebo-controlled, multicentre trials, included patients with hypervolaemic or euvolaemic hyponatraemia (serum sodium <135 mmol/L) associated with heart failure, cirrhosis or the syndrome of inappropriate antidiuretic hormone secretion. In both trials, patients receiving (in addition to standard medical treatment) tolvaptan 15-60 mg once daily (titrated according to response) for up to 30 days (n = 95 and 118) experienced significantly greater improvements than those receiving placebo (n = 89 and 114) for the co-primary endpoints of the change in average daily area under the curve for the serum sodium level from baseline to day 4 and from baseline to day 30. This beneficial effect of tolvaptan on serum sodium levels in SALT-1 and -2 was observed in patients with mild (serum sodium <135 mmol/L) and in those with marked (serum sodium <130 mmol/L) hyponatraemia at baseline. Tolvaptan was also superior to placebo in increasing serum sodium levels from baseline to day 7 in a subgroup of 323 patients with hyponatraemia (serum sodium <134 mmol/L) in the randomized, double-blind, multicentre EVEREST trials, which included patients who were hospitalized for worsening heart failure. Tolvaptan was generally well tolerated in clinical trials. The most frequently reported adverse events were thirst and dry mouth, which result from the pharmacodynamic effects of the drug.