[Therapeutic systems and drug delivery. 3. Transdermal therapeutic systems]

Following a short review of penetration of drugs through the skin (a bilayer membrane which consists of the stratum corneum and the viable epidermis), transdermal therapeutic systems (TTS) are described. These systems are special pharmaceutical preparations capable of delivery of some drugs (e.g. very potent drugs, with narrow therapeutic index, short biological half-life) via skin under well controlled conditions. After their application drug passes directly into the systemic circulation avoiding the effect of first-pass hepatic metabolism. At the same time, their advantages and disadvantages are presented. Finally, currently existing TTS in the market containing e.g. scopolamine (motion sickness), nitroglycerin (angina pectoris), estradiol (postmenopause), clonidine (hypertension) and systems in the development are briefly reported. These transdermal therapeutic systems are considered as a new approach to improve the usage of drugs in terms of better dosage control, increased safety and easier application.