A 9-year-old boy with newly diagnosed acute lymphoblastic leukaemia starts induction chemotherapy. Forty-eight hours later: uric acid 19 mg/dL, phosphate 9.2 mg/dL, potassium 6.4 mEq/L, calcium 6.0 mg/dL, creatinine 2.8 mg/dL. Allopurinol was given prophylactically. Which agent should now be added because it lowers the already-formed uric acid load?
- A Rasburicase, a recombinant urate oxidase ✓
- B Febuxostat, a non-purine xanthine oxidase inhibitor
- C Sodium bicarbonate infusion to alkalinise the urine
- D Calcium acetate to bind intestinal phosphate
Correct answer: A. Rasburicase, a recombinant urate oxidase
Explanation
Xanthine oxidase inhibitors, whether allopurinol or febuxostat, only block new uric acid synthesis and cannot clear urate already present. Rasburicase is a recombinant urate oxidase that converts existing uric acid into the far more soluble allantoin, making it the agent of choice when tumour lysis with marked hyperuricaemia is established. Urinary alkalinisation is avoided in tumour lysis because it promotes calcium phosphate deposition in tubules.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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