ABSTRACT
Introduction .................................................................................................................................... 137 General Overview of Fatty Alcohols and Fatty Acids on the Skin Permeation ........................... 138 Fatty Alcohols ................................................................................................................................. 139 Fatty Acids....................................................................................................................................... 144
Effect of Carbon Chain Length of Fatty Acids ........................................................................... 145 Saturated versus Unsaturated Fatty Acids .................................................................................. 145 The Number and Position of Double Bonds in Unsaturated Fatty Acids ................................ 146 Fatty Acid Esters.......................................................................................................................... 146 Chemical Modification of Drugs with Fatty Acids..................................................................... 147
Mechanism of Penetration Enhancement...................................................................................... 148 Lipid Disruption at the Intercellular Level: The Enhancer Disrupts Stratum
Corneum Lipid Organization, Making It Permeable to Drugs............................................. 148 Fatty Acids Form Solvated Complexes or Molar Addition Compounds and Permeate
through Skin Simultaneously with Drugs ............................................................................. 149 Fatty Acids Increase the Diffusivity and Partitioning of Drugs and Vehicles
through Stratum Corneum..................................................................................................... 150 Formulation Considerations........................................................................................................... 150
Enhancer Configuration in TDS ................................................................................................. 150 Fatty Alcohols and Acids in Transdermal Patches..................................................................... 151
Skin Irritation Potential................................................................................................................... 152 Summary ......................................................................................................................................... 153 References....................................................................................................................................... 154
Fatty alcohols, fatty acids, and their derivatives are used in a variety of skin and general healthcare products, to name a few: moisturizing creams, shampoos, hair products, shaving products, bath oils, lipsticks, and perfumed products. The wide usage of these
as topical ingredients implies that they are nontoxic and considered safe for topical use. Pimecrolimus 1% cream (Elidel1 cream), Tretinon cream (Renova1 cream), and Fluorouracil 0.5% cream are some examples of topical formulations employing fatty alcohols, or fatty acids, or both as dermatological ingredients. Alpha-lipoic acid, a ring containing fatty acid, is an active medicament for treating photo-damaged skin and is deemed safe as a topical agent. Fatty alcohols and fatty acids have been extensively investigated to characterize their interactions with stratum corneum (SC) and to describe their effects in modulating the skin barrier function.1 This chapter deals with the utility of fatty alcohols and fatty acids as promising skin penetration enhancers for topical and transdermal delivery of drugs. The role of vehicle or other ingredients on the enhancement effects of the topical or transdermal formulation and their skin irritation potential has also been discussed.
