Inability to interpret toxic salicylate levels in patients taking aspirin and diflunisal

Diflunisal, a nonsteroidal antiinflammatory drug, is not metabolized to the free salicylate moiety, but yields serum salicylate levels. We describe 2 patients who unexpectedly had toxic range serum salicylate levels while taking diflunisal and aspirin for rheumatoid arthritis