Allopurinol used in chronic gout works by inhibiting which enzyme?

• A Uricase
• B Phosphoribosyl pyrophosphate (PRPP) synthetase
• C Adenosine deaminase
• D Xanthine oxidase ✓

Explanation

Allopurinol is a structural analogue of hypoxanthine that competitively and irreversibly (via its active metabolite oxypurinol) inhibits xanthine oxidase, the enzyme that converts hypoxanthine to xanthine and xanthine to uric acid. This reduces uric acid production, leading to accumulation of hypoxanthine and xanthine, which are more soluble and readily excreted. Allopurinol is used for urate overproducers, frequent attacks, tophaceous gout, and urate nephropathy.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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