In its first part, this review paper discusses skin morphology and barrier
function of the stratum corneum for drug permeation after its transdermal a
dministration or topical application. Further, the paper presents the main
methods for overcoming the skin permeation barrier, which plays an importan
t role for transdermal drug administration. Focus is on the method of chemi
cal permeation enhancement. The chemical enhancers are categorised by their
chemical structure. Examples of the most effective enhancers are given for
the chemical groups of alcohols, amines and amides, polyalcohols, terpenes
, fatty acids and their esters, macro cyclic compounds, sulfoxides; tenside
s, and others, as e.g. soft enhancers.