Existence of a specialized absorption mechanism for cefadroxil, an aminocephalosporin antibiotic, in the human oral cavity

The absorption of cefadroxil, an aminocephalosporin antibiotic, from the oral cavity of healthy volunteers was examined. The buccal absorption test for cefadroxil at varying concentrations demonstrated the phenomenon of saturation in absorption behavior. Furthermore, absorption of cefadroxil was inhibited by the presence of another aminocephalosporin, cephalexin, but not by the structurally unrelated sulfisoxazole. The results suggest that aminocephalosporin antibiotics are absorbed from the human oral cavity via a specialized transport mechanism. On the other hand, cefadroxil absorption from hamster cheek pouch mucosa, a keratinized oral mucosa, took place in proportion to the initial concentration and was not influenced by the presence of cephalexin, indicating that the physicochemical interaction between these two aminocephalosporins in the luminal solution of the keratinized oral mucosa is practically negligible. Thus, the localization of the specialized absorption mechanism for cefadroxil was strongly suggested to be in the non-keratinized region in the human oral cavity.