Febuxostat efficacy in allopurinol-resistant tophaceous gout.

Allopurinol has been a standard hypouricemic agent for more than 40 years, but febuxostat, which is also a xanthine oxidase inhibitor, is now available. We present a case of tophaceous gout with uric acid levels that did not respond to prescription of very high doses of allopurinol or uricosuric agents. With febuxostat treatment, the patient had rapid and sustained reduction in her uric acid levels to target range. This case raises the possibility of currently unrecognized pharmacologic differences between allopurinol and febuxostat.