Allopurinol: Prevent uric acid production.

Allopurinol is a xanthine oxidase inhibitor, and it is true that its primary therapeutic action is to prevent uric acid production. Xanthine oxidase is the enzyme responsible for catalyzing the final steps of purine metabolism, converting hypoxanthine to xanthine and then xanthine to uric acid. By inhibiting this enzyme, allopurinol reduces the synthesis of uric acid, thereby lowering serum urate concentrations over time. This makes it particularly useful for patients with gout who are overproducers of uric acid or who have had uric acid kidney stones. It is important to understand that allopurinol is indicated for long-term prophylaxis of gout rather than treatment of acute attacks, since initiating or stopping allopurinol during an acute flare can mobilize urate crystals and worsen symptoms. In contrast, a uricosuric agent like probenecid enhances the renal excretion of uric acid rather than decreasing its production. Colchicine and NSAIDs such as indomethacin address acute inflammation without affecting uric acid synthesis or excretion. Knowing the distinction between drugs that reduce uric acid production and those that increase its excretion is essential for selecting the appropriate treatment based on the patient's underlying pathophysiology.