Febuxostat is used to treat gout in adults who were not treated successfully with or who are not able to take allopurinol (Aloprim, Zyloprim). Gout is a type of arthritis in which uric acid, a naturally occurring substance in the body, builds up in the joints and causes sudden attacks of redness, swelling, pain, and heat in one or more joints. Febuxostat is in a class of medications called xanthine oxidase inhibitors.