Effects of Tolvaptan vs Fluid Restriction in Hospitalized Subjects With Dilutional Hyponatremia

Inclusion Criteria: * Hyponatremia in clinically euvolemic or hypervolemic states, defined as serum sodium \< 130 mEq/L prior to randomization * Clinically significant symptoms of hyponatremia, defined as a CGI-S score between 3-6, inclusive * Female subjects of child bearing potential who agree to remain abstinent or to practice double-barrier forms of birth control from screening through 30 days following first dose on IMP Exclusion Criteria: * Women who are pregnant or breast feeding, and females of childbearing potential who are not using acceptable contraceptive methods (such as barrier contraceptives or methods that result in a failure rate of less than 1%) * Hyponatremia in hypovolemic states, defined as the presence of clinical and historical evidence of extracellular fluid volume depletion, including but not limited to skin turgor, orthostatic changes in blood pressure or heart rate, dry mucous membranes, or a response to IV saline challenge * Subjects who are likely to require prolonged hospitalization for reasons other than hyponatremia, eg. new femoral fracture, surgeries requiring extended recovery * Recent prior treatment for hyponatremia: hypertonic saline (including normal saline challenge) (within 8 hours of baseline) or urea, lithium, demeclocycline, conivaptan or tolvaptan (within 4 days of baseline). Includes any treatment, other than fluid restriction for the purpose of increasing serum sodium. * Hyponatremia symptoms of a severity (eg, CGI = 7) such t…