New tools and approaches for predicting skin permeability.

This article reviews some new mathematical models and techniques used to predict and understand percutaneous penetration and transdermal delivery. These models are also useful for various enhancement strategies that can be used in dermal-penetration and formulation development studies. If appropriate, biophysical techniques can be combined with these new mathematical models and statistical analyses and it will be possible to understand the factors affecting penetration of molecules through skin. These factors, or parameters, can then be used to control the penetration rate when effective transdermal delivery or therapy is required or targeted.