Effect of prophylaxis on gout flares after the initiation of urate-lowering therapy: analysis of data from three phase III trials

Background: Use of urate-lowering therapy (ULT), such as febuxostat or allopurinol, is recommended for the long-term management of hyperuricemia in patients with gout to reduce the incidence of acute flares. Because of the paradoxical relationship between early use of ULT and the increased incidence of gout flares, prophylaxis with either low-dose colchicine or NSAIDs has been recommended, although there have been concerns about the long-term prophylactic use of these agents.

Objectives: The present analysis examined flare rates during the 3 Phase III trials of febuxostat based on mean postbaseline serum urate (sUA) concentrations and duration of prophylaxis. Adverse events (AEs) were assessed by prophylaxis with colchicine or naproxen.

Methods: This investigator-initiated, post hoc reanalysis of data on gout flares from the 3 randomized, placebo-controlled, Phase III trials evaluated the proportion of patients requiring treatment for gout flares at 4-week intervals based on mean postbaseline sUA concentrations <6.0 and ≥ 6.0 mg/dL. The 3 trials enrolled males or females aged 18-85 years who had a diagnosis of gout and a baseline sUA concentration ≥ 8.0 mg/dL. Patients received ULT (febuxostat or allopurinol) or placebo for 6 months or 1 year and flare prophylaxis with colchicine 0.6 mg/d or naproxen 250 mg BID for 8 weeks or 6 months. The prophylactic regimen was chosen at the discretion of the investigator, based on renal function and known intolerance to either drug. Patients with an estimated creatinine clearance <50 mL/min were not to receive naproxen. AEs were summarized based on prophylaxis with colchicine or naproxen.

Results: The 3 trials enrolled a total of 4101 patients with gout. The majority were white (80.1%), male (94.5%), and obese (body mass index ≥ 30 kg/m(2)) (62.8%). The mean duration of gout ranged from 10.9-11.9 years, and the mean baseline sUA concentration ranged from 9.6-9.9 mg/dL. Flare rates increased sharply (up to 40%) at the end of 8 weeks of prophylaxis and then declined gradually, whereas flare rates were consistently low (range, 3%-5%) at the end of 6 months of prophylaxis. Mean postbaseline sUA concentrations were correlated with flare rates; by the end of each study, patients with a mean postbaseline sUA concentration <6.0 mg/dL had fewer flares than did those with a mean postbaseline sUA concentration ≥ 6.0 mg/dL. There were differences in rates of AEs between prophylaxis groups, but the rates did not increase with increased duration of prophylaxis.

Conclusion: This analysis of gout flare data from the 3 Phase III trials of febuxostat found that flare prophylaxis for up to 6 months during the initiation of ULT appeared to provide greater benefit than flare prophylaxis for 8 weeks, with no increase in AEs.