Allopurinol is a medication that is primarily used to treat gout and reduce uric acid levels. It prevents uric acid production by blocking activity of an enzyme that converts purines to uric acid. Allopurinol is an antagonist of some chemotherapeutic agents, and, as such, may reduce some effects. Allopurinol mouthwash has been evaluated in patients with cancer for its potential local effects in the prevention and management of mucositis.