In TLS prevention, which uric acid–lowering therapy rapidly reduces uric acid levels and is used in high‑risk patients?

• A. Allopurinol rapidly lowers existing uric acid levels.
• B. Probenecid rapidly lowers uric acid levels.
• C. Rasburicase rapidly reduces uric acid levels.
• D. Febuxostat rapidly lowers uric acid levels.

Answer: (C)

Rapid reduction of uric acid is crucial in TLS prevention to prevent uric acid nephropathy after tumor cell breakdown. Rasburicase is a recombinant urate oxidase that converts uric acid to allantoin, a more soluble compound that is easily excreted by the kidneys. This enzymatic action provides a swift drop in uric acid levels, which is why it’s used in high‑risk TLS patients who already have elevated uric acid or large tumor burden.

In contrast, agents that inhibit uric acid formation, like allopurinol and febuxostat, prevent the production of new uric acid but do not quickly reduce existing uric acid levels. Probenecid increases renal excretion of uric acid but does not achieve the rapid reduction TLS requires and isn’t the standard approach there.

So, the fast-acting option for high‑risk TLS is rasburicase. Be aware that rasburicase can pose risks in patients with G6PD deficiency and related hypersensitivity reactions, so appropriate testing and monitoring are important.