Final answer:
Allopurinol is used to treat (A) gout, which is a painful condition caused by the accumulation of uric acid crystals in the joints, and it works by reducing the production of uric acid.
Step-by-step explanation:
Allopurinol is used to treat the condition known as gout. Gout is a form of arthritis characterized by the accumulation of uric acid crystals in the joints, leading to painful inflammation. This condition can occur when the body produces too much uric acid or when the kidneys don't excrete it efficiently. Certain foods high in nitrogenous bases, such as tea, coffee, and chocolate, which contain purine-like compounds called xanthines, are recommended to be avoided by individuals with gout.
Allopurinol works by acting as a competitive inhibitor of the enzyme xanthine oxidase, thereby reducing the production of uric acid. It is structurally similar to hypoxanthine, the natural substrate of xanthine oxidase, and therefore competes with it at the active site of the enzyme.