Rasburicase is used in tumor lysis syndrome. Its mechanism of action and key contraindication are:

• A Uricosuric agent; contraindicated in CKD due to uric acid renal deposition
• B Xanthine oxidase inhibitor (more potent than allopurinol); contraindicated in renal failure
• C Recombinant urate oxidase (rasburicase) converts urate to allantoin (soluble); contraindicated in G6PD deficiency due to hydrogen peroxide byproduct ✓
• D Recombinant PEGylated uricase; contraindicated in gout with tophi (paradoxical flares)

Explanation

Rasburicase is a recombinant urate oxidase that enzymatically oxidizes uric acid to allantoin, which is 5–10 times more soluble and renally excreted; this rapidly lowers uric acid levels in tumor lysis syndrome. The reaction produces hydrogen peroxide as a byproduct, which in patients with G6PD deficiency (lacking adequate glutathione reduction capacity) causes severe hemolytic anemia and methemoglobinemia — rasburicase is absolutely contraindicated in G6PD deficiency. Pegloticase is a PEGylated version used in refractory gout.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.