The FAST trial
The ongoing Febuxostat versus Allopurinol Streamlined Trial (FAST) has provided data about undertreatment with allopurinol and the effects of increasing the dose. The prospective, randomized, open-label study is comparing the cardiovascular safety of allopurinol and febuxostat in patients with symptomatic hyperuricemia. It enrolled patients who were on allopurinol in normal clinical practice. To enter, patients had to have a serum urate level below 6 mg/dL. If patients’ levels were not below 6 mg/dL, investigators increased the dose of allopurinol to try to reach that target (Semin Arthritis Rheum. 2014 Aug;44[1]:25-30).
“Basically, this part of the study is a dose-escalation trial for efficacy,” Dr. Mandell said. “Of 400 patients taking allopurinol, 36% still had a urate above 6 [mg/dL]. ... If you uptitrated the dose, 97% of people were able to get to 6. Uptitration works. You just actually need to do it.” The results indicate that a 100-mg increase in allopurinol dose decreases serum urate by about 1 mg/dL.
Allopurinol hypersensitivity and chronic kidney disease
Patients with chronic kidney disease may have increased risk of allopurinol hypersensitivity. For a while, researchers postulated that oxypurinol, the active component of allopurinol, built up and caused toxicity in some patients with chronic kidney disease. As a result, researchers suggested adjusting the dose for patients with chronic kidney disease.
One problem with this approach is that only about 20% of patients with chronic kidney disease would reach the treatment target with the suggested doses, Dr. Mandell said. “You are exposing them to some potential risk with a very low chance of actually getting any efficacy at all,” he said.
Furthermore, allopurinol hypersensitivity behaves like an allergic reaction, not a toxicity reaction. Small studies suggest that starting allopurinol at a low dose and slowly increasing the dose may be safe in patients with chronic kidney disease. Allopurinol is not nephrotoxic, and some data indicate that it may be nephroprotective, he said.
Dr. Mandell reported that in recent years he was a clinical investigator and consultant for Horizon and a consultant for Takeda and Ardea/AstraZeneca/Ironwood.
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