Hypouricemic action of diflunisal in gouty patients: in vitro and in vivo studies.

Sixteen hyperuricemic gouty patients were treated with diflunisal, a novel salicylate, 500 mg BID. Serum and urine uric acid along with uric acid clearances were studied before and after a 7-day treatment. A clear hypouricemic action was observed, but 2 different mechanisms of action were seen when overexcretor patients and normoexcretor patients were analyzed separately. In overexcretors an allopurinol-like action was evident, whereas in normoexcretors a uricosuric action occurred. In vitro experiments showed a competitive inhibition of xanthine-oxidase exerted by diflunisal at low concentrations.