Membrane transporters (potentially) involved in the CNS distribution of cefadroxil. Several references were used to inform this schematic representation [16, 39–41]. There is much debate regarding the isoforms and membrane localization of MRPs at the BBB. There is, though, considerable evidence for some MRPs having an apical distribution clearing substrates to blood as depicted. There is also functional evidence for the probenecid-inhibitable efflux of cefadroxil from brain cells , the nature of which is uncertain but may include OAT, MRP and/or OATP transporters. BL represents the basolateral membrane, AP the apical membrane, and EP the ependyma.