Multicenter, Randomized, Double-blind, Placebo-controlled Study to Evaluate the Efficacy and Safety of Oral Lixivaptan Capsules in Subject With Euvolemic Hyponatremia

Inclusion Criteria: * Written informed consent * Men or women aged 18 or older * Diagnosis of euvolemic hyponatremia (120 ≤ Na+\<130 mEq/L) * Hospitalized or willing to be admitted to a monitored setting for approximately the first 48 hours of treatment Exclusion Criteria: * Pregnant or breast-feeding women, or women planning to become pregnant or to breastfeed * Symptomatic hyponatremia (e.g., lethargy, coma, seizures, changes in mental status attributable to hyponatremia) * Acute or transient hyponatremia (e.g., associated with head trauma or postoperative state) * Hyponatremia in hypovolemic states. Hypovolemic hyponatremia is defined as the presence of clinical evidence of extracellular fluid volume depletion * Hyponatremia as a result of any medication that can safely be withdrawn * Hyponatremia due to hypothyroidism or adrenal insufficiency * Diagnosis of psychogenic polydipsia * Receiving within 7 days of enrollment, other medication for treatment of hyponatremia specifically: demeclocycline, lithium carbonate, urea, or conivaptan * Use of radiotherapy and chemotherapy within 2 wks of randomization * Likely to require, or to receive IV saline for correction of symptomatic or asymptomatic severe hyponatremia during the course of the study * Supine systolic arterial blood pressure of ≤ 90 mmHg * Serum creatinine \>3.0 mg/dL * History of uncontrolled type 2 diabetes mellitus * Severe pulmonary artery hypertension: patients whose condition is expected to deteriorate wit…