In TLS management, rasburicase is preferred in which patients?

• A. Low-risk TLS.
• B. Allopurinol-resistant TLS.
• C. High-risk TLS or allopurinol-resistant TLS.
• D. Only after kidney transplant.

Answer: (C)

Rasburicase is preferred when rapid control of uric acid is needed to prevent uric acid–related kidney injury in tumor lysis syndrome. It works by converting existing uric acid into allantoin, which is water-soluble and easily excreted, so uric acid levels fall quickly. Allopurinol only stops new uric acid from forming and does not reduce already present uric acid promptly, which is insufficient in patients with a high tumor burden or impaired kidney function. Therefore, in high-risk TLS—or when TLS does not respond to allopurinol (allopurinol-resistant TLS)—rasburicase is the best choice. In lower-risk TLS, hydration and monitoring with allopurinol may be adequate. Rasburicase is not limited to post-kidney transplant scenarios; use depends on TLS risk and response, with attention to potential safety considerations such as G6PD deficiency.