Allopurinol and febuxostat were found to be associated with a higher risk of hypersensitivity reactions when compared to colchicine, according to the results of a recently published population-based study.

In order to determine the risk of hypersensitivity reactions associated with allopurinol and febuxostat use, the study authors identified patients who received a new prescription for allopurinol, febuxostat, or colchicine from a random sample of Medicare beneficiaries between the years of 2006 and 2012. “We used multivariable-adjusted Cox regression analyses to compare the hazard ratio (HR) of incident hypersensitivity reactions with allopurinol or febuxostat use vs colchicine use; separate analyses were done in people exposed to allopurinol,” the authors explained. Additionally, propensity-matched analyses (5:1 ratio) were performed in order to compare new allopurinol vs new febuxostat use. 

The study authors reported crude incidence rates of hypersensitivity reactions (per 1000 person-years) for allopurinol, febuxostat, and colchicine to be 23.7, 30.7, and 25.6, respectively. Findings of the analysis revealed allopurinol and febuxostat were associated with significantly higher HRs of hypersensitivity reactions compared with colchicine. HRs of hypersensitivity reactions were reported to be 1.32 for allopurinol (95% CI, 1.10-1.60), 1.54 for febuxostat (95% CI, 1.12-2.12), and 2.17 for febuxostat+colchicine (95% CI, 1.18-3.99). No significant difference was observed between febuxostat and allopurinol in the propensity-matched analysis (HR, 1.25; 95% CI, 0.93-1.67). 

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Findings of the analysis also revealed significantly higher HRs of hypersensitivity reactions with allopurinol for female patients (1.32, 95% CI, 1.17-1.48), patients with diabetes (HR, 1.21; 95% CI, 1.00-1.45), and those who received a start dose of ≥300mg/day (HR, 1.27; 95% CI, 1.12-1.44) compared with those who received <200mg/day.  

Additionally, it was reported that 69% of hypersensitivity reactions occurred in the outpatient setting. “Our findings provide new knowledge regarding hypersensitivity reactions to these commonly used medications for the treatment of gout that can inform clinicians and patients alike starting these medications,” the study authors concluded.

Reference

Singh JA, Cleveland JD. Hypersensitivity reactions with allopurinol and febuxostat: a study using the Medicare claims data. Annals of the Rheumatic Diseases. Published Online First: 05 February 2020. doi: 10.1136/annrheumdis-2019-216917