Febuxostat is preferred over allopurinol in patients with moderate chronic kidney disease for long-term urate-lowering therapy. The key pharmacokinetic advantage of febuxostat in CKD is:

• A Febuxostat is a prodrug activated in the kidney and thus retains activity even with low GFR
• B Febuxostat inhibits xanthine oxidase non-competitively, making its efficacy independent of urine output or GFR
• C Febuxostat has a uricosuric component that compensates for reduced renal xanthine clearance in CKD
• D Unlike allopurinol and its active metabolite oxypurinol (which rely predominantly on renal elimination), febuxostat is primarily metabolised by the liver (CYP1A2, 2C8, UGT enzymes) and its metabolites are eliminated by both faeces and urine, requiring no dose adjustment in mild-moderate CKD ✓

Explanation

Allopurinol is metabolised to oxypurinol, which is the primary active metabolite and is almost entirely renally eliminated (>90%). In CKD, oxypurinol accumulates markedly, increasing the risk of allopurinol hypersensitivity syndrome (AHS) and myelosuppression — mandating dose reduction. Febuxostat, in contrast, is primarily metabolised by hepatic oxidative (CYP1A2, CYP2C8) and glucuronidation (UGT1A1, UGT1A3, UGT1A9) pathways; its inactive glucuronide metabolites are excreted via both bile/faeces (~45%) and urine (~45%), so dose adjustment is not required until eGFR <30 ml/min. Febuxostat has no uricosuric action.

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

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Written and medically reviewed by the StethoPrep medical team.