Transdermal drug delivery in vitro using diffusion cells.

The assessment of percutaneous absorption of molecules is a very important step in the evaluation of any dermal or transdermal drug delivery system. In order to perform percutaneous drug absorption studies, it is essential that the methods are standardized and that the integrity of the skin is monitored and maintained to ensure that the data obtained are valid and relevant. Reproducible data on percutaneous absorption in humans are as well required to predict the systemic risk from dermal exposure to chemicals, such as hazardous substances at the workplace, agrochemicals and cosmetic ingredients. In vitro and animal models provide important tools for screening a series of drug formulations, evaluation of skin permeation enhancing properties and mechanism of action of the carrier systems and estimation of rank of skin transport for a series of drug molecules. In this review, we have summarized in vitro testing of skin absorption using static Franz-type diffusion cells.