The Effect of Allopurinol on Renal Function.

BACKGROUND: Hyperuricemia is associated with development of gout, hypertension, and renal disease. The impact of allopurinol, a urate-lowering therapy, on renal function is unclear, especially in patients with chronic kidney disease who are at higher risk of hypersensitivity reaction.

OBJECTIVES: The aim of this study was to determine the effect of allopurinol on kidney function in hyperuricemic male veterans.

METHODS: This is a retrospective cohort study using pharmacy, medical, and laboratory records of veterans enrolled at the Veterans Administration New York Harbor Healthcare System, Brooklyn campus. Fifty patients with hyperuricemia defined as a serum uric acid greater than 7 mg/dL (average of ~9 mg/dL), newly started on allopurinol for any reason, with evidence of treatment compliance, were matched by age, race, sex, and estimated glomerular filtration rate (EGFR) to 50 hyperuricemic control subjects. The retrospective cases were observed from October 2000 until November 2006, at which time there was a change in the laboratory analyzer, making further comparisons inappropriate.

RESULTS: On average, patients treated with a mean 221 (SD, 96) mg/d dose of allopurinol achieved 11.9 mL/min higher GFR (95% confidence interval, 4.8-11.9 mg/d dose; P = 0.01) than did the control group. Treatment effect was found to depend on the initial EGFR, as indicated by the significant treatment by initial EGFR interaction (P = 0.004) and increased with a higher initial EGFR. The allopurinol-treated group had a 0.10 mg/dL lower final creatinine level (95% confidence interval, 0.003-0.20 mg/dL; P = 0.04) than did the control subjects, adjusted for initial creatinine and age. The average length of follow-up was 3.4 years. There were 5 mild adverse events in the treated cases.

CONCLUSIONS: Treatment of hyperuricemic patients with allopurinol over an average of 3.4 years resulted in a significant improvement of kidney function in this male cohort from the Veterans Administration Healthcare System. Clinicians should consider this potential benefit of allopurinol in the treatment of patients with hyperuricemia, those with overall maintained renal function.