Efficacy and Safety of Extended Release and Immediate Release Febuxostat in Participants With Gout

The drug being tested in this study is called febuxostat. Febuxostat is being tested to decrease and maintain serum urate in people who have gout. This study will look at serum urate levels in people who take febuxostat extended release (XR) capsules compared to febuxostat immediate release (IR) capsules and placebo. The study will enroll approximately 1750 patients. Participants will be randomly assigned (by chance) to one of the five treatment groups-which will remain undisclosed to the patient and study doctor during the study (unless there is an urgent medical need): * Febuxostat 40 mg XR * Febuxostat 80 mg XR * Febuxostat 40 mg IR * Febuxostat 80 mg IR * Placebo (dummy inactive pill) - this is a tablet that looks like the study drug but has no active ingredient. All participants will be asked to take one capsule at the same time each day throughout the study, and will be asked to call an interactive voice response system any time they are having a gout flare up. In addition to study medication, participants will also take 0.6 mg of colchicine every day or every other day, or naproxen 250 mg twice a day and lansoprazole 15 mg once a day to prevent gout flare ups. This multi-centre trial will be conducted in the United States. The overall time to participate in this study is up to approximately 4 months and participants will make up to 7 visits to the clinic.