What is the mechanism of action (MAO) of Allopurinol?

• A. Inhibits xanthine oxidase
• B. Inhibits uric acid reabsorption
• C. Stimulates uric acid production
• D. Enhances renal clearance of uric acid

Answer: (A)

Allopurinol is a medication that primarily functions by inhibiting xanthine oxidase, an enzyme critical in the metabolic pathway that converts hypoxanthine to xanthine and then to uric acid. By inhibiting this enzyme, Allopurinol effectively reduces the production of uric acid in the body. This reduction is particularly beneficial for patients suffering from conditions associated with high levels of uric acid, such as gout or certain types of kidney stones.

The significance of this mechanism lies in its impact on decreasing uric acid levels, thereby preventing the formation of urate crystals that can lead to pain and inflammation in gout attacks. It is not involved in inhibiting uric acid reabsorption, stimulating its production, or enhancing its renal clearance, which are pathways not associated with the action of Allopurinol. The main therapeutic effect stems from its ability to directly affect uric acid synthesis through the blockade of xanthine oxidase activity.