Table 6.

Main features of allopurinol and rasburicase

Allopurinol: a preventive uricogenesis agent	Rasburicase: an uricolytic agent
It competitively inhibits xanthine oxidase, so prevents further uric acid synthesis	It catalyzes the oxidation of already synthetized uric acid into allantoin
It does not directly alter acid uric levels, so its action is slower and gradual, within 24 - 48 h and reaches a maximum after 7-10 days	Its action is faster in controlling uricemia, within 4 h
It may increase creatinine levels	It may reduce creatinine levels and urea nitrogen, by improving renal function
It increases precursors of uric acid, such as xanthine, less soluble in urine than uric acid. It may impair renal function and improve stone formation.	It does not require alkalinization, so calcium phosphate's stones formation is less probable.
Its formulation is oral since 1966. Since 1999 a new intravenous formulation (not yet available in Italy) was introduced in USA	An intravenous formulation is available
It needs an adjustment of doses if patient has renal impairment, because its active metabolite, oxypurinol, is excreted in urine.	No adjustment of doses is necessary if patient has renal or hepatic impairment. In renal failure, allantoin may accumulate, but it is not toxic.
It has drug-drug interaction with very common agents (chlorpropamide, 6-mercaptopurine, azathioprine, dicumarol, cyclosporine, thiazide diuretics)	No drugs interactions are referred