A Study to Assess the Efficacy, Safety and Pharmacokinetics of Intravenous Conivaptan (Vaprisol®) in Pediatric Subjects With Euvolemic or Hypervolemic Hyponatremia

Inclusion Criteria: * Subject is euvolemic or hypervolemic hyponatremia upon clinical presentation * Subject has serum sodium value ≥ 115 mEq/L (115 mmol/L) and \< 130 mEq/L (130 mmol/L) during the 24 hours preceding inclusion into the study * Female subject of childbearing potential must have a negative serum pregnancy test and must be premenarchal, surgically sterile or must practice a method of birth control Exclusion Criteria: * Female subject is pregnant or lactating * Subject has a body mass index (BMI) \< the 3rd percentile or \> the 97th percentile for their age and stature according to the World Health Organization; Body mass index-for-age percentiles charts for boys and girls ages 2 to 20 * Subject has clinical evidence of volume depletion, dehydration or hypovolemia * Subject with hypovolemic hyponatremia or transient causes of hyponatremia that are likely to resolve during the time of study participation * Subjects with a cause of hyponatremia that is most appropriately corrected by alternative therapies * Subject is expected to receive emergent treatment for hyponatremia during the treatment period of the study * Subject has clinical evidence of hypotension * Subject has uncontrolled hypertension \> the 99th percentile for their age * Subject has uncontrolled bradyarrhythmias or tachyarrhythmias requiring emergent pacemaker placement or treatment * Subject has untreated severe hypothyroidism, hyperthyroidism or adrenal insufficiency * Subject has known urinary…