The FDA has approved Samsca (tolvaptan tablets, from Otsuka), a once-daily oral vasopressin V2-receptor antagonist, for the treatment of patients with clinically significant hypervolemic and euvolemic hyponatremia, including those with heart failure, cirrhosis, and syndrome of inappropriate anti-diuretic hormone (SIADH). This approval was based on results from two double-blind, placebo-controlled, multi-center studies in 424 patients with euvolemic or hypervolemic hyponatremia. Patients were treated for 30 days with Samsca or placebo. The primary endpoint of these studies was the average daily area under the curve (AUC) for change in serum sodium from baseline to Day 4 and baseline to Day 30. Compared to placebo, Samsca caused a statistically greater increase in serum sodium during both periods in both studies.
Samsca is expected to be available June 2009 in 15mg and 30mg dosage strengths.