Impact of serum albumin levels on the body fluid response to tolvaptan in chronic kidney disease patients

Purpose Tolvaptan exerts an aquaretic effect by blocking vasopressin V2 receptor. Although tolvaptan ameliorates body fluid retention even in patients with chronic kidney disease (CKD), predictors of body fluid reduction induced by tolvaptan remain unclear. We, therefore, examined the clinical parameters associated with the effect of tolvaptan on fluid volume in CKD patients. Methods Twelve CKD patients (stage 3–5) with fluid retention were treated with tolvaptan in addition to conventional diuretic treatment. Patients were divided into low and high responders by the median change in total body water (TBW) for 1 week measured by a bioimpedance analysis (BIA) device, and clinical parameters were compared between the groups. Results The body weight significantly decreased by 2.0 ± 2.3 kg ( p = 0.005), but the estimated glomerular filtration rate (eGFR) was not significantly changed (16.9 ± 11.9 vs. 17.4 ± 12.4 mL/min/1.73 m 2 , p = 0.139) after 1 week. The BIA showed that the intracellular water (ICW) decreased by 6.0% ± 4.7% ( p < 0.001), the extracellular water (ECW) decreased by 6.7% ± 5.4% ( p = 0.001), and the TBW decreased by 6.3% ± 4.9% (median value − 6.02%, p < 0.001). The serum albumin level in the high responders was significantly lower than in the low responders (2.3 ± 0.5 vs. 3.3 ± 0.8 g/dL, p = 0.013). Significant partial correlations adjusted for the eGFR were observed between the baseline serum albumin level and changes in the ICW ( r = 0.440, p = 0.048), ECW ( r = 0.593, p = 0.009) and TBW ( r = 0.520, p = 0.020). Conclusions Serum albumin levels predict the body fluid response to tolvaptan in CKD patients. Tolvaptan may be a promising therapeutic option for ameliorating body fluid retention, especially in patients with hypoalbuminemia.