Allopurinol is a medication used to treat gout and certain types of kidney stones by lowering high levels of uric acid in the body. It works by inhibiting xanthine oxidase, an enzyme responsible for the production of uric acid. By reducing uric acid levels, allopurinol helps to prevent gout attacks and long-term joint damage. It is also used to manage elevated uric acid levels in patients undergoing cancer treatment, as these therapies can cause a rapid increase in uric acid due to cell breakdown.