Taking allopurinol without dose adjustment in patients with severe renal impairment significantly increases the risk of toxicity due to drug accumulation.
Always adjust dose downward in CrCl <30 mL/min to prevent accumulation.
Screen for HLA-B*5801 allele in high-risk populations to assess hypersensitivity risk.
Monitor CBC, LFTs, and renal function frequently.
Discontinue immediately if rash or hypersensitivity symptoms appear.
Allopurinol is metabolized to oxypurinol, its active metabolite, which is primarily excreted by the kidneys. In severe renal impairment, reduced glomerular filtration rate leads to accumulation of oxypurinol, prolonging and intensifying xanthine oxidase inhibition and increasing exposure to potential toxic effects.
Elevated risk of severe hypersensitivity reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis), acute kidney injury exacerbation, bone marrow suppression, and gastrointestinal disturbances; may also worsen gout flares due to incomplete uric acid control.
Reduce initial dose to 50-100 mg/day based on creatinine clearance (e.g., <10 mL/min: max 100 mg/day); monitor serum oxypurinol levels, renal function, and signs of hypersensitivity closely; consider alternatives like febuxostat or probenecid if severe impairment persists.
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