Objective To assess the effect of allopurinol dose/duration on the risk of renal failure in the elderly with allopurinol use.

Methods We used the 5% random Medicare claims data from 2006 to 2012. Multivariable-adjusted Cox regression analyses assessed the association of allopurinol dose/duration with subsequent risk of developing incident renal failure or end-stage renal disease (ESRD) (no prior diagnosis in last 183 days) in allopurinol users, controlling for age, sex, race and Charlson–Romano comorbidity index. HRs with 95% CIs were calculated. Sensitivity analyses considered a longer baseline period (365 days), controlled for gout or used more specific codes.

Results Among the 30 022 allopurinol treatment episodes, 8314 incident renal failure episodes occurred. Compared with 1–199 mg/day, allopurinol dose of 200–299 mg/day (HR 0.81; 95% CI 0.75 to 0.87) and ≥300 mg/day, 0.71 (0.67 to 0.76), had significantly lower hazard of renal failure in multivariable-adjustment model, confirmed in multiple sensitivity analyses. Longer allopurinol use duration was significantly associated with lower hazards in sensitivity analyses (365-day look-back; reference, <0.5 year): 0.5–1 year, 1.00 (0.88, 1.15); >1–2 years, 0.85 (0.73 to 0.99); and >2 years, 0.81 (0.67 to 0.98). Allopurinol ≥300 mg/day was also associated with significantly lower risk of acute renal failure and ESRD with HR of 0.89 (0.83 to 0.94) and 0.57 (0.46 to 0.71), respectively.

Conclusions Higher allopurinol dose is independently protective against incident renal failure in the elderly allopurinol users. A longer duration of allopurinol use may be associated with lower risk of incident renal failure. Potential mechanisms of these effects need to be examined.