Allopurinol is a well-established xanthine oxidase inhibitor widely used in the management of hyperuricemia, gout, tumor lysis syndrome, and uric acid nephrolithiasis. This review provides a comprehensive overview of its pharmacology, mechanism of action, pharmacokinetics, clinical efficacy, safety profile, and emerging insights from recent clinical and translational studies. Despite being in clinical use for over five decades, allopurinol remains the first-line urate-lowering therapy worldwide due to its proven efficacy, favorable safety profile, and cost-effectiveness. Beyond its classical role in inhibiting xanthine oxidoreductase, increasing evidence highlights additional therapeutic effects, including antioxidant and anti-inflammatory activities. The structural similarity of allopurinol to purine compounds contributes to its ability to scavenge reactive oxygen species, particularly hydroxyl radicals. Moreover, uric acid itself has been proposed to function as a physiological antioxidant, prompting further investigation into the broader redox-modulating properties of allopurinol. Following administration, allopurinol is rapidly metabolized to oxypurinol (4,6-dihydroxypyrazolo3,4-dpyrimidine), its primary active metabolite, which plays a major role in sustained xanthine oxidase inhibition. Comparative studies suggest that both allopurinol and oxypurinol contribute to free radical scavenging, although their relative antioxidant capacities may differ. Despite its widespread use, important clinical concerns remain, particularly regarding hypersensitivity reactions and its use in patients with chronic kidney disease. Therefore, ongoing research is essential to better understand its extended biological effects and optimize its safe clinical application.
khaldoon et al. (Wed,) studied this question.