Known brand names include Zyloprim.
A pill that lowers uric acid to prevent gout attacks, high uric acid during cancer treatment, and some repeat kidney stones. It blocks the enzyme that makes uric acid, and any rash is a reason to stop it, because rare skin reactions can be fatal.
Labeled use. Adults and children with leukemia, lymphoma, or solid tumors receiving cancer therapy that raises uric acid.
Sources: [1]
Labeled use. Adults with recurrent calcium oxalate stones and high urinary uric acid despite lifestyle changes.
Sources: [1]
The usual first-line urate-lowering drug for gout: inexpensive, and usable in chronic kidney disease when started low and titrated slowly. Febuxostat is an alternative when allopurinol is not tolerated or HLA-B*58:01 is positive, and probenecid is a uricosuric option for people with normal kidney function. It does not treat an acute flare; colchicine, NSAIDs, or corticosteroids do. For tumor lysis prevention, rasburicase is preferred when uric acid is already high or the risk is very high.
A xanthine oxidase inhibitor and structural analogue of hypoxanthine. It blocks the steps from hypoxanthine to xanthine and from xanthine to uric acid without disrupting purine synthesis. Its active metabolite oxypurinol also inhibits xanthine oxidase and is thought to mediate most of the effect. About 90% is absorbed; half-lives are about 1 to 2 hours for allopurinol and 15 hours for oxypurinol, which the kidneys eliminate.
The label does not describe a narrow therapeutic index or direct dosing by measured blood levels of the drug. Dosing targets serum uric acid, not drug levels.
Sources: [1]
Doses come from the FDA label. Study tool, not for clinical decisions.
Gout starting doses by eGFR: above 60, no change; above 30 to 60, 50 mg daily; above 15 to 30, 50 mg every other day; 5 to 15, 50 mg twice weekly; below 5, 50 mg once weekly. Increase by 50 mg/day every 2 to 4 weeks to the uric acid target. Cancer therapy: eGFR 10 to 20, 200 mg/day; below 10, 100 mg/day; with dialysis, 100 mg once every 24 hours or 50 mg every 12 hours. Monitor kidney function closely.
No labeled dose change. Monitor liver enzymes periodically in pre-existing liver disease, check them if anorexia, weight loss, or pruritus develop, and stop allopurinol if they are elevated.
Sources: [1]
No specific antidote. Allopurinol and oxypurinol are dialyzable, but whether hemodialysis or peritoneal dialysis helps after an overdose is unknown.
Sources: [1]
Animal findings suggest possible fetal harm, and allopurinol and oxypurinol cross the placenta. Limited human data show no clear pattern of adverse outcomes, although among about 50 published pregnancies, 2 infants had major malformations. Advise pregnant patients of the potential risk.
Sources: [1]
Allopurinol and oxypurinol pass into human milk. Because of possible serious reactions in the infant, avoid breastfeeding while taking it and until 1 week after the final dose.
Sources: [1]
Established only for hyperuricemia from cancer therapy, in about 200 pediatric patients: 100 mg/m² orally every 8 to 12 hours, which is 10 mg/kg/day, up to 800 mg/day, with fluids of at least 100 mL/m²/hour. Not established for gout, recurrent calcium oxalate stones, or inborn errors of purine metabolism. Not studied with eGFR below 20 mL/min or on dialysis.