In tumor lysis syndrome, what is the primary role of rasburicase?

• A. Rasburicase rapidly metabolizes uric acid to allantoin, lowering uric acid quickly.
• B. Rasburicase inhibits xanthine oxidase to reduce uric acid production.
• C. Rasburicase enhances uric acid excretion through the kidneys.
• D. Rasburicase prevents uric acid formation by blocking purine metabolism.

Answer: (A)

In tumor lysis syndrome the danger comes from a sudden surge of uric acid from rapidly destroyed tumor cells. Rasburicase works by enzymatically converting uric acid into allantoin, a compound that is far more soluble and readily excreted by the kidneys. This rapid degradation lowers circulating uric acid quickly, helping prevent uric acid nephropathy and acute kidney injury.

Other strategies would address uric acid differently: inhibiting xanthine oxidase would reduce production of new uric acid but doesn’t rapidly lower existing high levels; increasing renal excretion is not the direct action of rasburicase—though the product is excreted, the key effect is degradation of uric acid itself. Blocking purine metabolism would prevent formation of uric acid in the first place, which is a different approach than what rasburicase provides.