Beneficial role of tolvaptan in the control of body fluids without reductions in residual renal function in patients undergoing peritoneal dialysis.

The V2 receptor antagonist tolvaptan has been approved for volume control in heart-failure patients in Japan. Tolvaptan increases renal blood flow, and so the present study was designed to ascertain whether tolvaptan could be a useful diuretic for volume control without reducing residual renal function (RRF) in peritoneal dialysis (PD) patients. Tolvaptan was administered in 15 PD patients (15 mg daily). Urine volume, body weight, and blood pressure were monitored. Urinary excretion of urea nitrogen Na+, the osmolality of plasma and urine, and peritoneal and renal Kt/V were analyzed before and after tolvaptan treatment. In 11 of 15 patients, urine volume increased to more than 400 mL daily. A significant increase in diluted urine was observed, as indicated by a reduction in the specific gravity or osmolality of urine (or both). Urinary excretion of urea nitrogen, and Na+ was significantly increased. Increases in renal Kt/V were observed, but peritoneal Kt/V was unchanged. Singnificant increase in creatinine clearance was also observed. These data suggest that tolvaptan not only stimulates water diuresis, but also natriuresis, without reducing RRF in PD patients. Hence, tolvaptan could be a beneficial tool for the control of body fluid and maintenance of RRF in PD patients.