ABSTRACT
The main reason to apply an active substance (or a drug) on the skin is for in situ therapy. Mineral substances such as the famous terra sigillata were used during the Roman Empire to cure super cial skin conditions. Similarly, different compositions containing, inter alia, hot or warm vegetable mass, which is suspected to relieve pain, have been utilized for centuries in Asia, Africa, and Europe
5.1 Introduction........................................................................................................................... 137 5.2 Skin Structure, Composition, and Biofunctionality.............................................................. 138
5.2.1 Skin as a Barrier ....................................................................................................... 138 5.2.2 Biotransformations in the Skin Layers ..................................................................... 139 5.2.3 Biotransformations on the Skin Surface ................................................................... 139 5.2.4 Skin Flora ................................................................................................................. 140
5.3 Dermal and Transdermal Drug Delivery.............................................................................. 141 5.3.1 Transcutaneous Drug Delivery Routes ..................................................................... 141 5.3.2 Transdermal Drug Transport .................................................................................... 141 5.3.3 Drug Diffusion.......................................................................................................... 142 5.3.4 Vehicle Composition and Drug Absorption.............................................................. 143 5.3.5 Transdermal Therapeutic Systems ........................................................................... 144
5.4 Hydrogels for Topical Application ........................................................................................ 145 5.4.1 Hydrogels for Dermal Application ........................................................................... 147 5.4.2 Hydrogels for Transdermal Application ................................................................... 148
5.5 Hydrogel-Functionalized Textile Materials .......................................................................... 149 Abbreviations ................................................................................................................................. 151 Symbols.......................................................................................................................................... 151 References ...................................................................................................................................... 151
(Ling, 1998). The topical delivery of compounds to the surface and deeper layers of the skin and the transdermal delivery of pharmacologically active substances is an issue of great interest for both professionals and consumers. The cosmetic industry is performing continuous research on sunscreens, insect repellents, and beauty products. The pharmaceutical sector studies topical antiinfectives and emollients for the skin surface. Antibiotics, antiin ammatory drugs, corticosteroids, and uorouracil are intended to act in the inner skin tissues. Skin delivery systems are being evaluated to maintain the concentration of drugs, such as nicotine, antihypertensives, scopolamine, nitroglycerine, testosterone, and antiarthritics, in the central compartment. During the last four decades, some drug forms have been developed for delivery of active substances to systemic circulation. Since the 1960s, transdermal drug delivery has been developed systematically (Scheuplein, 1978), and the skin as an application site for drug delivery systems has been recognized.
