Aims: The purpose of the present study was to investigate the role of efflux transporters on the intestinal absorption of amtolmetin guacyl (MED-15). Main methods: The effects of P-glycoprotein (P-gp), multiple resistance-associated protein 2 (MRP2), and breast cancer resistance protein (BCRP) inhibitors on intestinal absorption amount of MED-5 (tolmetin-glycine amide derivative), the metabolite formed from MED-15 in the intestinal epithelial cells were studied in the in vitro everted gut sac experiments. Moreover, the in situ single-pass intestine perfusion was adopted to clarify the role of efflux transporters in excreting MED-5 in knockout mice. The plasma concentration of MED-5 and tolmetin, the metabolite formed from MED-5 was determined in Bcrp1 knockout mice and wild-type mice. Key findings: BCRP inhibitor Ko143 (50 mu M and 100 mu M) significantly increased the intestinal absorption amount in jejunum, ileum and colon (p<0.05). However, no effect was observed in the presence of P-gp inhibitor verapamil and MRP2 inhibitor MK571 in each intestinal segment. Furthermore, the plasma concentration MED-5 and tolmetin, metabolites of MED-15. increased 2-fold and 4-fold, respectively, in Bcrp1 knockout mice compared with wild-type mice after the single-pass perfusion of small intestine with MED-15. Significance: It may be concluded that BCRP plays an important role in the intestinal efflux of MED-5 and limits the bioavailability after oral administration of MED-15. (C) 2013 Published by Elsevier Inc.