# Purine Excretion

**Purine Excretion** describes the series of reactions used to excrete the free purine bases, hypoxanthine and guanine, in the event that they are not salvaged (see [Purine Salvage](/content/view/4414/index.html)).

The pathway begins with the purine bases, **hypoxanthine** and **guanine**, which are then converted into **xanthine**. Xanthine is then converted to **uric acid**, in a reaction catalyzed by **xanthine oxidase**. The xanthine oxidase enzyme can be inhibited by the drugs **allopurinol** and **febuxostat**. These drugs prevent the formation of uric acid and are commonly used to treat **gout**.

**Uric acid clearance** by the kidney plays a major role in purine excretion, and clearance is enhanced by the drugs **probenecid** and **rasburicase**. In contrast, **aspirin** has been shown to reduce clearance of uric acid.