Effects of Renal Function on Urinary Excretion and Serum Concentration of Uric Acid in Patients Treated with Febuxostat for Chronic Kidney Disease

Background: Febuxostat is recommended for lowering serum uric acid (sUA) concentration in chronic kidney disease (CKD) patients with hyperuricemia. However, it remains uncertain how febuxostat af-fects associations between several laboratory variables related to glomerular filtration and renal tubular reabsorption of uric acid. Methods: We retrospectively analyzed the records of 148 patients with CKD and hyperuricemia: 122 were treated with febuxostat, and 26 were not. Clinical and laboratory variables were used to calculate estimated glomerular filtration rate (eGFR), fractional excretion of uric acid (FEUA), and estimated 24-h urinary excretion of uric acid (eEUA). We examined correlations of those variables and compared pa-tients who did and did not receive febuxostat.Results: eGFR and FEUA were significantly inversely regardless of febuxostat-treatment status. eGFR was significantly inversely correlated with sUA in patients who received febuxostat, but not in those who did not. Similarly, there was a significant positive correlation between FEUA and eEUA only in pa-tients treated with febuxostat.Conclusions: FEUA increased as eGFR decreased in our patients. Febuxostat changed correlation pat-terns for clinical and laboratory variables. Additional administration of uricosuric agents might help further lower sUA by increasing FEUA and eEUA in patients treated with febuxostat. (J Nippon Med Sch 2022; 89: 360?367)