Question of the Day

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USMLE Step 2 Question of the Day

February 27, 2023

What is the mechanism of action of allopurinol?

Correct Answer: 

A. Inhibits uric acid formation

Explanation:

Allopurinol inhibits uric acid formation (answer A). Allopurinol is an isomer of hypoxanthine (a naturally occurring purine in the body) and it inhibits xanthine oxidase. This enzyme is responsible for the successive oxidation of hypoxanthine and xanthine resulting in the production of uric acid, the product of purine metabolism. Allopurinol decreases both uric acid formation and purine synthesis.

Colchicine binds to tubulin (answer C) and Indomethacin inhibits cyclooxygenase (answer E).

Quick Concepts:

Allopurinol – mechanism of action

  • Competitive inhibitor of xanthine oxidase
  • Decreases uric acid production

Summary:

Allopurinol is a competitive inhibitor of xanthine oxidase which ultimately decreases uric acid production.

Correct Answer: 

A. Inhibits uric acid formation

Explanation:

Allopurinol inhibits uric acid formation (answer A). Allopurinol is an isomer of hypoxanthine (a naturally occurring purine in the body) and it inhibits xanthine oxidase. This enzyme is responsible for the successive oxidation of hypoxanthine and xanthine resulting in the production of uric acid, the product of purine metabolism. Allopurinol decreases both uric acid formation and purine synthesis.

Colchicine binds to tubulin (answer C) and Indomethacin inhibits cyclooxygenase (answer E).

Quick Concepts:

Allopurinol – mechanism of action

  • Competitive inhibitor of xanthine oxidase
  • Decreases uric acid production

Summary:

Allopurinol is a competitive inhibitor of xanthine oxidase which ultimately decreases uric acid production.


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