Allopurino land its active metabolite, inhibits the enzyme xanthine oxidase, blocking the conversion of the oxypurines hypoxanthine and xanthine oxidase through negative feedback result in a decrease in the concentration of uric acid in the serum and urine. Allopurinol also facilitate the incorporation of hypoxanthine and xanthine into DNA and RNA, leading to feedback inhibition of de novo purin synthesis and a decrease in serum uric acid concentration as a result of an increase in nucleotide concentration.

prevent increase of uric acid in patient receiving chemotherapy

Febuxostat, a xanthine oxidase inhibitor,achieves its therapeutic effect by decreasing serum uric acid. Febuxostat does mot inhibits other enzymes involved in purine and pyrimidine synthesis and metabolism at therapeutic concentration

For treatment and relief of pain in attack of acute gouty arthritis

Colchicine interrupts the cycle of mono-sodium urate crystal deposition in joint tissues and the resultant inflammatory response that initiates and sustains an acute attack. Colchicine decrease leukocyte chemotaxis and phagocytes and inhibits the formation and the release of chemotactic glycoprotein that is produced during phagocytosis of urate crystals. It also inhibit urate crystal deposition, which is enhanced by a low pH in tissues, probably by inhibiting oxidation of glucose and subsequent lactic acid production in leukocytes.