Comparative risk of retinal microvascular disorders in patients with gout initiating febuxostat versus allopurinol: a population-based cohort study.

Despite recent accumulation on cardiovascular (CV) safety data on xanthine oxidase inhibitors (XOIs) among gout patients, assessment has been largely limited to macro- than micro-vascular disorders, prompting the investigation on the latter outcome. Therefore, we aimed to compare the risk of retinal microvascular disorders between allopurinol and febuxostat initiators among gout patients. Using the 2011-2019 Korean National Health Insurance service database, we conducted a cohort study on gout patients initiating allopurinol or febuxostat. The primary outcome was a composite of retinal microvascular disorders. After 1:1 propensity-score (PS) matching in non-diabetic (non-DM) and diabetic (DM) subgroups, pooled and subgroup-specific hazard ratios (HRs) and 95% confidence intervals (CIs) were reported, comparing allopurinol and febuxostat. We included 118,376 PS-matched pairs of febuxostat and allopurinol initiators (mean 57.3 years, 83.7% male; 89,642 pairs in non-DM and 28,734 pairs in DM subgroup). During a mean follow-up of 223 days, the incidence rate per 100 person-years of the primary outcomes was 0.88 among allopurinol users and 0.93 among febuxostat users. The corresponding HR (95% CI) was 0.98 (0.83-1.15). The HR (95% CI) was 0.94 (0.76-1.15) in non-DM subgroup and 1.05 (0.80-1.39) in DM subgroup. The result for DM retinopathy also showed a similar risk (HR 0.86, 95% CI 0.67-1.11). In this large population-based cohort study on patients with gout, we did not find any difference in the risk of retinal microvascular disorders between allopurinol and febuxostat initiators.