Correlation between cell- and tissue-based in vitro models for drug permeability screening with in vivo situation: Modeling and functional extrapolation

The usefulness of an in vitro permeability assay is directly related to its ability to capture the fundamental aspects of drug passage through in vivo membranes. Various approaches can be undertaken to establish the connection between in vitro permeability and some more or less directly related in vivo measure of drug permeability. This chapter outlines some strengths and limitations of direct empirical correlations between in vitro and in vivo data. It also summarizes the use of physiologically based pharmacokinetic models as a tool to further enlighten physiological mechanisms underlying the in vivo permeability of drugs.