The Impact of Penetration Enhancers on Transdermal Drug Delivery System: Physical and Chemical Approach
There is considerable interest in the skin as a site of drug application for both local and systemic effect. However, the skin, in particular the stratum corneum, possesses a formidable barrier to drug penetration thereby limiting topical and transdermal bioavailability. Skin penetration enhancement techniques have been developed to improve bioavailability and to increase the range of drugs for which topical and transdermal delivery is a viable option. Transdermal drug delivery system (TDDS) having objective to deliver the therapeutic moiety via the skin into the systemic circulation for its therapeutic effect. This route provides many advantages over other routes as avoiding first pass hepatic metabolism, decrease side effects, GI effects and increased bioavailability. The skin, in particular stratum corneum provides protective barrier that prevents the loss of physiologically essential substances and provide resistance to penetration and it is the rate limiting step in percutaneous absorption. So, various penetration enhancers have been used to promote the percutaneous absorption of a number of drugs. Several research studies have been done in transdermal permeation studies using various enhancers for several drug moieties. This review high lights the detailed role of penetration enhancers and describes the classification of different penetration enhancers with their mechanism of action and properties. Most of the earlier reviews have focused on a certain selected aspect of transdermal drug delivery. This review presents a comprehensive account of various aspects of drug delivery by transdermal route including the various chemical and physical penetration enhancers.