We investigate the inhibitory effect of marketed drugs for treatment of inflammatory bowel disease (IBD) such as ulcerative colitis (UC) and Crohn’s disease (CD) on the uptake transporters of peptide transporter 1 (PEPT1), which are up-regulated under the inflamed condition. The uptake transport of glycylsarcosine, a typical substrate for PEPT1, was reduced to 60% only by 5-aminosalicylate at the clinically relevant concentration among tested marketed drugs in PEPT1 transfected HEK293 cell lines. These findings suggest that the inhibition of PEPT1, which were up-regulated in inflamed or non-inflamed site on UC and CD patients, contribute to the clinical effect of commercially available drugs for IBD patients through the inhibition of uptake of antigenic proinflammatory oligopeptides such as formyl-methionine (Met)-leucine (Leu)-phenylalanine (Phe) via PEPT1.