Review on Transdermal Drug Delivery Systems

Abstract

ISSN: 2348-9782 During the past decades, intensive studies have focused on the technologies in drug delivery, and with the rapid developments and explorations in technologies, traditional drug delivery means are being replaced by the more effective and advanced ones. The creation of transdermal drug delivery system (TDDS) has been one of the most sophisticated and innovative approaches of drug deliveries. The transdermal drug delivery system has attracted considerale attention because of its many potential advantages, including better patient compliance, avoidance of gastrointestinal disturbances, hepatic first-pass metabolism and sustained delivery of drugs to provide steady plasma profiles, particularly for drugs with short half-lives, reduction in systemic side effects and enhanced therapeutic efficacy [1][2][3][4][5][6].Recently, transdermal drug delivery system (TDDS) has become a more and more important approach to administering drugs. Based on its advantages, which are not achievable by other modes of administration, many researchers are dedicated to the study of it, and have made great progress. Although the skin offers a painless interface for systemic drug delivery, it also presents limitations which are mainly caused by the stratum corneum. In this work, we state the increasingly impact of TDDS, discuss the limitations of it, and last but not least, we highlight the methods for overcoming these limitations by using permeation enhancers, microneedles, iontophoresis.Despite these advantages, most of the transdermal candidates have low permeability. The drugs administered across skin should have the three constraining characteristics: appropriate partition coefficient, low molecular mass (<500Da), and small required dose (upto milligrams) [3]. The limitations of transdermal drug delivery are caused by skin which protects against and is impermeable to foreign molecules. The human skin is consisted of two main layers: the layer of epidermis and the layer of dermis. Stratum corneum is the epidermis's outermost layer that composed of stratified keratinocytes, multiple lipid bilayers of ceramidas, fatty acids, cholesterol and cholesterol esters. Stratum corneum provides an extremely effective physical barrier for the control of drug penetration [2,[7][8][9][10]. Therefore, attempts to overcome this skin barrier is presently an important area of pharmaceutical and toxicological research. The techniques that weaken the barrier have included permeation enhancers , microneedles and iontophoresis [69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84]. Chemical permeation enhancersIn the last 50 years, a large number of chemical permeation enhancers (CPEs) which are defined as substances that interact with the major constituents of skin barrier, stratum corneum, to promote penetration of drugs into skin.The ideal enhancer should have the following conditions: 1. Non-pharmacological activities. 2. Nontoxic,. Rapid-acting with predictable and reproducible activity. 4. When removed from the skin...