American Board of Internal Medicine (ABIM) Certification Practice Exam

For patients experiencing tumor lysis syndrome, how soon can rasburicase reduce serum urate levels after administration?

1. Within 1 hour

2. Within 4 hours

3. Within 12 hours

4. Within 24 hours

The correct answer is: Within 4 hours

Rasburicase is an enzyme used to lower serum urate levels in patients at risk of tumor lysis syndrome, especially during the treatment of malignancies. After administration, rasburicase acts quickly to catalyze the breakdown of uric acid into allantoin, a more soluble and easily excreted compound. Clinical studies indicate that significant reductions in serum urate levels can be observed within a short period, typically within 4 hours after administration. This rapid onset of action makes rasburicase particularly effective in managing hyperuricemia associated with tumor lysis syndrome, allowing for timely intervention to prevent potential complications associated with elevated uric acid levels, such as acute kidney injury. While urate levels may continue to decline after this initial phase, the most notable impact occurs within the 4-hour window, making this timeframe critical in the context of acute management of this condition.