Allopurinol is an oral medication typically used to prevent uric acid and calcium oxalate stones in dogs. It is also used off-label to treat leishmaniasis and gout in dogs and other species. Side effects are uncommon but may involve stomach upset. Caution must be taken when allopurinol is used in conjunction with certain other medications. It should not be used in pets with liver or kidney dysfunction or in red-tailed hawks.