Oral route of drug administration is the simplest and widely used route of drug therapy, however, is not always feasible as a large proportion of drugs are poorly water soluble requiring special technique to deliver the drug per oral. Furthermore, many oral drugs fail to achieve sufficient plasma concentration owing to extensive first pass metabolism hence require frequent dosing, leading to various adverse effects. The design and development of new drug delivery systems with the intention of enhancing the efficacy and decreasing the associated adverse effects of such drugs is an ongoing process in pharmaceutical research. Transdermal delivery represents an alternative to oral delivery of such drugs. They are supposed to decrease adverse effects, improve efficacy and patient compliance. Although Transdermal drug delivery has made an important contribution to medical practice since its inception, but has yet to fully achieve its potential as an alternative to oral delivery and hypodermic injections because of several associated problems. Only a limited number of drugs with low dose, low molecular weight and high octanol-water partition coefficients are amenable to administration by transdermal route, because of the anatomical structure of the barrier layer of skin. In the last few years strategies have been developed in order to increase the permeability of the skin which include physical, electrical, and chemical and biochemical techniques. Among these, modification of permeability by chemical method is most widely used owing to economical, simple and rapid, however increased permeation enhancement, typically correlated with increased skin irritation. It is desirable to develop a transdermal system that does not require the use of irritating and toxic chemical enhancers to facilitate drug permeation through the skin.
