XDH and chronic kidney disease: Allopurinol, a purine inhibitor of xanthine oxidase (XO) conventionally used for urate-lowering therapy (ULT) to inhibit uric acid synthesis, was suggested to slow a reduction in renal function compared with the control group in a 12-month, prospective, randomized controlled trial (RCT) in 54 hyperuricemic patients with CKD [10] and delayed a reduction in renal function compared with the control group in a 24-month, prospective RCT in 113 patients with CKD stage 3 [11].