XDH and hyperuricemia: To test the hypothesis that Yokuininto, a Kampo medicine that has been used for osteoarthritis [13] or rheumatoid arthritis [14], can be applied to treat hyperuricemia and gouty arthritis, we investigated the uric acid modulating effects of Yokuininto on serum level of uric acid, XO inhibiting activity, and OAT3 and GLUT9 transporter activities.