The renal clearance of riboflavin was determined in three human subjects at various serum concentrations of the vitamin with and without prior administration of probenecid. Renal clearances of riboflavin exceeded (up to three times) the endogenous creatinine clearances, which indicates that riboflavin excretion involves renal tubular secretion. The clearance of riboflavin was less at low than at high serum concentrations of the vitamin, characteristic of a saturable tubular reabsorption process. Probenecid decreased the renal clearance of riboflavin, and this effect was directly related to the serum concentration of the inhibitor. The serum protein binding of the vitamin was essentially constant (60%) over the concentration range encountered and was unaffected by the presence of probenecid.
- Probenecid, effect—riboflavin, renal clearance, plasma protein binding
- Riboflavin, renal clearance, man—probenecid effect