Permeability is one of the key factors determining how a drug is absorbed, distributed and eliminated. Most conventional small molecule drugs permeate through cell membranes via passive diffusion or are actively transported by transporter proteins. The function of these drug transporters can be affected by co-administered drugs, and thus transporter studies should be included in drug-drug interaction evaluation.

Our fifth e-book explains the fundamental differences between passive drug permeation and active transportation and the clinical relevance of these phenomena. The most relevant drug transporters, divided into efflux and uptake transporters, are listed in the book alongside with brief assay descriptions on how to study their functions for evaluating drug-drug interaction risk. To book also describes how basic permeation studies can be conducted utilising Caco-2 or MDCKII cell monolayers.