Studies of interactions among drugs in man at the renal level: Probenecid and sulfinpyrazone

The interactions between the uricosuric agents probenecid and sulfinpyrazone were studied in subjects with gout by means of renal clearance experiments. It was found that in both acid and alkaline urine, probenecid markedly inhibited renal tubular secretion of sulfinpyrazone without significantly altering the maximal uric acid clearance observed with each drug alone. It was also observed that probenecid inhibits the tubular secretion of the p‐hydroxy metabolite of sulfinpyrazone. The implications of these findings are discussed in terms of multiple "cascade" renal interactions among administered drugs and their respective metabolites.