Molecular mechanisms of biliary excretion of cefditoren and the effects of cefditoren on the expression levels of hepatic transporters.

Cefditoren, a third generation cephalosporin antibiotics, has been used in clinics extensively. Previous results have indicated that cefditoren is excreted into bile as unchanged form. To investigate whether canalicular membrane transporters of hepatocytes were involved in the biliary excretion of cefditoren, we examined the hepatobiliary disposition of cefditoren using probenecid, novobiocin and verapamil as inhibitors of Mrp2, Bcrp and P-gp respectively in perfused rat livers. The values for the hepatic extraction ratio had no statistical significance, whereas cumulative biliary excretion rates of cefditoren were significantly reduced to 43.8% and 79.5% over 25 min in the perfused probenecid and novobiocin rats, respectively. We further investigated the effects of cefditoren on the expression of hepatic transporters by RT-PCR and Western blot after oral administration of cefditoren one week. The expression levels of Mrp2, Bcrp, Oat2 mRNA were markedly increased, while P-gp and Oct1 mRNA were decreased. In concordance with RT-PCR results, Mrp2 expression level increased by Western blotting. These results indicate that Mrp2 and Bcrp may be involved in the biliary excretion of cefditoren. Cefditoren can up-regulate the expression levels of Mrp2, Bcrp and Oat2, and down-regulate P-gp and Oct1 mRNA expression. These results provide important data for drug-drug interactions.