Skin permeability methodologies for topical absorption prediction

Abstract

Understanding of skin absorption processes is needed not only for assessment of the safety aspects of chemicals, other xenobiotics, or cosmetic formulations but also to determine drug release of substances to the different skin strata and further to systemic circulation. In the field of pharmaceutical sciences, drug delivery to the skin is gaining more and more interest, owing to the high acceptance by patients. In this regard, two different cases have to be distinguished: local delivery to selected skin layers (e.g., antimycotics) and systemic delivery (e.g., hormones). In the context of bioavailability assessment, knowledge on the absorption behavior of the active compound is essential. For ethical reasons, fundamental skin absorption data can normally not be obtained by conducting in vivo studies. Therefore, other techniques must be used to obtain the desired information. One option to obtain these data is the use of in vitro penetration and permeation models.