The effects of three anti-inflammatory propionic acid derivatives (ketoprofen, fenbufen and flurbiprofen) on renal excretion of sulfamethizole were investigated in rats, in order to clarify the mechanisms involved. The clearance ratio of sulfamethizole was markedly decreased after ketoprofen or fenbufen infusion, while flurbiprofen had no effect on sulfamethizole excretion. From these results, it is speculated that the decrease of renal excretion of sulfamethizole caused by ketoprofen or fenbufen is mainly due to competitive interaction between sulfamethizole and ketoprofen or fenbufen at the renal secretory level.
