ABSTRACT
Introduction ...................................................................................................................................... 17 Fatty Acids......................................................................................................................................... 18
Effect of Carbon Chain Length..................................................................................................... 18 Saturated and Unsaturated Fatty Acids ........................................................................................ 20 Branched versus Unbranched Fatty Acids................................................................................... 20 Position of Double Bond ............................................................................................................. 21 Geometric Isomers........................................................................................................................ 21 Number of Double Bonds............................................................................................................ 21
Fatty Alcohols ................................................................................................................................... 22 Fatty Acids versus Fatty Alcohols................................................................................................. 24
Terpenes ........................................................................................................................................... 24 Pyrrolidones...................................................................................................................................... 26 Surfactants......................................................................................................................................... 28 Conclusions ...................................................................................................................................... 29 References......................................................................................................................................... 29
Transdermal drug delivery offers many advantages over the conventional routes of administration. Elimination of hepatic first-pass effects, reduced side effects through
optimization of the blood concentration profile, and extended duration of activity are some of the advantages of transdermal delivery. However, the highly organized structure of the stratum corneum forms an effective barrier to the penetration of a diverse range of agents, which must be modified if poorly penetrating drugs are to be administered. The stratum corneum consists of dead, anucleate, keratinized cells embedded in a lipid matrix. The drug molecules have two major routes of passage through the stratum corneum, passage between the cells (intercellular route) and passage across the corneocytes (transcellular route).
