Allopurinol

Allopurinol is a medication that lowers uric acid by inhibiting xanthine oxidase. It is used to prevent gout and treat certain forms of hyperuricemia.

Xanthine oxidase: An enzyme that converts hypoxanthine to xanthine and xanthine to uric acid. Allopurinol inhibits this enzyme, reducing uric acid production.
Gout: An inflammatory arthritis caused by deposition of monosodium urate crystals in joints and tissues. Long-term allopurinol reduces urate levels to prevent recurrent attacks.
Hyperuricemia: An abnormally high concentration of urate in the blood. It is the biochemical condition allopurinol is prescribed to reduce.
Probenecid: A uricosuric medication that lowers serum urate by reducing its reabsorption in the kidneys. It increases urate excretion instead of inhibiting uric acid production.
Purine metabolism: The biochemical pathways that synthesize, recycle, and break down purine nucleotides. Allopurinol acts on the final stages of purine breakdown.
Tumor lysis syndrome: A potentially life-threatening metabolic complication caused by rapid destruction of cancer cells. Allopurinol can prevent uric acid accumulation during high-risk cancer treatment.
Monosodium urate: The urate salt that forms crystals in tissues when local conditions permit. Its crystals cause gout, while sustained urate lowering helps dissolve deposits.
Pegloticase: An intravenous enzyme medication that converts uric acid into a more soluble compound. It is reserved for severe gout that remains uncontrolled despite oral therapies.
Oxypurinol: The active metabolite of allopurinol that persists longer in the body and inhibits xanthine oxidase. This metabolite accounts for much of the sustained enzyme inhibition.
Lesch–Nyhan syndrome: An inherited disorder of purine salvage caused by deficiency of hypoxanthine-guanine phosphoribosyltransferase. Allopurinol can treat its excess uric acid, but not its neurologic features.

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