Efficacy and safety of oral tolvaptan in patients undergoing hemodialysis: a Phase 2, double-blind, randomized, placebo-controlled trial

Background. Loop diuretics are used to manage fluid retention in patients with end-stage kidney disease undergoing hemodialysis (HD). This randomized, double-blind, placebo-controlled, Phase 2 trial evaluated the efficacy and safety of tolvaptan, a vasopressin V-2 receptor antagonist, in Japanese HD patients. Methods. A total of 124 patients (24-h urine volume >= 500 mL) on thrice-weekly HD were randomized to receive oral tolvaptan 15 mg/day (n=40), tolvaptan 30 mg/day (n=40) or placebo (n=44) for 24 weeks. Efficacy endpoints were change from baseline in 24-h urine volume, total fluid removal by HD per week and interdialytic weight gain (IDWG). Safety was assessed via the incidence of treatment-emergent adverse events (TEAEs). Results. At treatment end, the difference (95% confidence interval) from the placebo group in the mean change from baseline in 24-h urine volume was significant in the tolvaptan 15 mg {429.1 mL [95% confidence interval (CI) 231.0, 627.2]; P<0.0001} and 30mg [371.6 mL (95% CI 144.1, 599.2); P=0.0017] groups. The mean changes from baseline in total fluid removal by HD and IDWG were not significantly different in the tolvaptan groups versus the placebo group. Although the proportion of patients with TEAEs was lower in the placebo group (77.3%) than in the tolvaptan groups (92.3%), tolvaptan was safe and well-tolerated during the study period. Conclusions. Tolvaptan significantly sustained diuretic action for 24 weeks in HD patients but did not reduce total fluid removal by HD per week and IDWG to the same extent.