A Trial to Investigate the Efficacy and Safety of Orally Administered Tolvaptan (OPC-41061) in Patients With Chronic Renal Failure Undergoing Hemodialysis or Hemodiafiltration

Inclusion Criteria: * Chronic renal failure requiring hemodialysis or hemodiafiltration 3 times a week * Daily urine volume of ≥ 500 mL/day * Male or female patients age 20 to 80 years, inclusive * Use of one of the specified contraceptive methods until 4 weeks after final IMP administration * Capable of providing their own written informed consent prior to any trial-related procedures being performed Exclusion Criteria: * Patients with a complication of urinary impairment due to urinary tract stricture, urinary calculus, tumor in urinary tract, or other cause * Patients with NYHA class IV heart failure * Patients with impaired hepatic function(chronic hepatitis, drug-induced liver injury) * Patients with serious ischemic heart disease who are judged by the investigator or subinvestigator to be inappropriate for inclusion in the trial * Patients with serious arrhythmia who are judged by the investigator or subinvestigator to be inappropriate for inclusion in the trial * Patients with serious secondary hyperparathyroidism(intact parathyroid hormone \> 500 pg/mL) * Patients who are concomitantly undergoing peritoneal dialysis * Patients with a history of cerebrovascular disease or coronary artery disease within 4 weeks prior to informed consent, a history of hypersensitivity to any ingredient of tolvaptan or benzazepine derivatives such as mozavaptan hydrochloride or a history of impaired hepatic function(chronic hepatitis, drug-induced liver injury) * Patients with any of the following abnormal laboratory values: hemoglobin \< 8.0 g/dL, total bilirubin \> 3.0 mg/dL, ALT (GPT) or AST (GOT) \> 2 times the upper limit of the reference range, serum sodium \> upper limit of the reference range, serum sodium \< 125 mEq/L, or serum potassium \> 6.0 mEq/L * Patients who are unable to sense thirst or who have difficulty with fluid intake * Patients who have received OPC-41061 in history. * Participation in any other clinical trial or post-marketing clinical study within 4 weeks prior to informed consent for the present trial * Female patients who are pregnant, possibly pregnant, or nursing * Patients otherwise judged by the investigator or subinvestigator to be inappropriate for inclusion in the trial