Background/Purpose: American College of Rheumatology (ACR) guidelines recommend use of either allopurinol or febuxostat as first-line approaches to urate lowering therapy in gout. Prior studies of managed care cohorts have shown that patients are commonly switched to febuxostat before their allopurinol dose has been optimized. While each is effective, their cost differential (8 cents/pill compared to 5 dollars/pill at our facility) suggests there may be good reason to favor allopurinol use within a health system. To identify potential areas for improvement for allopurinol and febuxostat use, we sought to better understand current febuxostat prescribing practices at our facility among patients with chronic gout who were initially on allopurinol.

Methods: Data were extracted from the local pharmacy prescription database to identify all patients ≥ 18 years of age, seen at our facility, and prescribed febuxostat between 1/1/13 and 8/31/16. We conducted a retrospective chart review to identify the daily dose of allopurinol before febuxostat prescription. Additionally, the type of prescribing physician (rheumatologist, non-rheumatologist), reason for prescribing febuxostat (inadequate response to other medications, kidney dysfunction, allopurinol hypersensitivity), uric acid level, estimated glomerular filtration rate (GFR) at time of switch, presence of tophi, and demographic data were recorded.

Results: Sixty-four patients with chronic gout were switched from allopurinol to febuxostat. Forty-two patients were switched due to adverse drug events (most commonly rash, n = 17 or gastrointestinal symptoms, n = 8) and 22 due to inadequate response.

Table 1. Characteristics of Patients Switched to Febuxostat Due to Inadequate Response to Allopurinol

Table 2. Allopurinol Dosing Prior to Switching to Febuxostat According to Estimated Glomerular Filtration Rate

Conclusion: In our facility, most of the patients were prescribed febuxostat due to adverse effects from allopurinol. Among those switched due to inadequate response, almost two-thirds had a dose of 300 mg/day or less.