Allopurinol Adherence in US Patients With Gout

Background/Objective Gout is the most common inflammatory arthritis, and its morbidity can be substantially reduced through urate-lowering therapy. However, adherence to allopurinol—the most common urate-lowering therapy—is notoriously poor. Prior studies have not fully elucidated factors associated with allopurinol adherence, particularly psychosocial factors. Methods We used 2018–2021 data from the Medical Expenditure Panel Survey, a national longitudinal survey on health care expenditures and utilization. We calculated the medication possession ratio (MPR) for allopurinol for participants with gout and categorized each as follows: no allopurinol fills, low adherence (MPR ≤0.8), or high adherence (MPR >0.8) to allopurinol. We used multivariable logistic regression to identify factors associated with high adherence, using person-year as the unit of measure and accounting for clustering for participants who contributed more than 1 person-year. Results The analyses included 919 respondents (1453 person-years), representing a weighted total of 15,084,439 person-years. Across all years, 27.4% had no allopurinol fills, 37.4% had low adherence, and 35.2% had high adherence. In multivariable models for high adherence, Black race (odds ratio, 0.49; 95% confidence interval, 0.33–0.73, compared with White) and residence in the South US region (odds ratio, 0.54; 95% confidence interval, 0.35–0.82, compared with Northeast) were negatively associated with high adherence. Conclusions Black race and residing in the Southern US were associated with lower allopurinol adherence among gout patients. Interventions to improve adherence, particularly among Black patients in the South, are needed to maximize the potential benefits of allopurinol.