Everted rat intestinal sacs as an in vitro model for assessing absorptivity of new drugs.

An in vitro model that utilizes everted rat intestinal sacs was evaluated for assessing the absorptivity of several analogs of potential drug substances prior to formulation work and clinical trials. This model not only is a useful qualitative tool for assessing absorptivity of structurally related compounds but also yields some insight into the process involved in drug absorption. Notwithstanding the complexities involved in the absorption processes, the data support the hypothesis that the absorption of organic electrolytes mainly takes place by the partitioning of the unionized species into the lipoidal membranes and then diffusion.