Which statement best describes uric acid–lowering therapy used in TLS prevention?

• A. Aggressive hydration alone.
• B. Allopurinol or rasburicase.
• C. Electrolyte replacement without uric acid-lowering therapy.
• D. Avoid monitoring uric acid levels.

Answer: (B)

In TLS prevention, the goal is to prevent uric acid from building up and precipitating in the kidneys, which can cause acute kidney injury after rapid tumor cell breakdown. Allopurinol and rasburicase achieve this directly. Allopurinol works by inhibiting xanthine oxidase, so less uric acid is produced from purines. Rasburicase, on the other hand, rapidly converts existing uric acid into a soluble compound (allantoin) that’s easier to excrete. In prophylaxis, allopurinol is commonly started to limit new uric acid formation, while rasburicase is used when there is already hyperuricemia or when a rapid reduction is needed. Hydration and careful electrolyte management are important supportive measures, but they don’t directly lower uric acid. Monitoring uric acid levels is essential to gauge therapy effectiveness.