USMLE Step 1


Biochemical Pathways

Purine Excretion
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Purine Excretion

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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).

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.

Find Purine Excretion and more Biochemical Pathways among Pixorize's visual mnemonics for the USMLE Step 1 and NBME Shelf Exams.