An Extension Follow-up Trial to Evaluate the Long-term Safety of Children and Adolescent Participants With Euvolemic or Hypervolemic Hyponatremia

"Tolvaptan 3.75-, 7.5-, 15-, and 30-mg spray-dried tablets. Dosage: Depending on age and weight, Tablet (3.75 mg - 60 mg daily). Frequency: Once daily.~Duration: Participants may be eligible to receive short-term or long-term optional tolvaptan treatment at any time during their participation in the trial, with one or more treatment cycles over a 6-month period."