Transdermal Drug Delivery System- Design and Evaluation

The human skin is a readily accessible surface for drug delivery. Skin of an average adult body covers a surface of approximately 2 m 2 and receives about one-third of the blood circulating through the body. Over the past three decades, developing controlled drug delivery has become increasingly important in the pharmaceutical industry. The human skin surface is known to contain, on an average, 10-70 hair follicles and 200-250 sweat ducts on every square centimeters of the skin area. It is one of the most readily accessible organs of the human body. The potential of using the intact skin as the port of drug administration to the human body has been recognized for several decades, but skin is a very difficult barrier to the ingress of materials allowing only small quantities of a drug to penetrate over a period of time. During the past decade, the number of drugs formulated in the patches has hardly increased, and there has been little change in the composition of the patch systems. Modifications have been mostly limited to refinements of the materials used. The present article reviews the selection of drug candidates suitable to be formulated as Transdermal system and the methods of evaluation. Keywords:- Transdermal; Drug Delivery; TDDS