Transdermal drug delivery specializes in continuing to search for new methods that can effectively and painlessly deliver larger molecules in therapeutic quantities to overcome the difficulties associated with the oral route, likely poor bioavailability due to the first pass effect and the tendency to produce rapid blood level spikes. Transdermal delivery can improve the therapeutic efficacy and safety of drugs by more precise way but spatial and temporal placement within the body is required to reduce both the size and number of doses necessary to achieve the objective of systemic medication through topical application. Modulation of formulation excipients and addition of chemical enhancers can increase drug flux but that is not sufficient to ensure delivery of pharmacologically effective concentration of the drug therefore, several new active rate controlled TDDS technologies electrically-based, structure-based, velocity-based, Vesicular carriers, i.e. Liposomes, museums, transfersomes represent widely exploited class of novel delivery systems for topical applications with immunological approaches for new vaccine design. Noninvasive vaccination onto the skin using these novel carriers could improve vaccination programs because the procedure requires no specially trained personnel and may avoid risk associated with needle prick. These delivery systems act as adjuvant to enhance the immunogenicity of antigens, which otherwise induce 'weak' immune response when applied topically. Transdermal delivery have been developed and commercialized for the delivery of ‘troublesome’ drugs Skin harbors a wide variety of immune cells and elicit a strong immunological response, when it comes in contact with any immunogen. Skin shows specific (immunity) against non-specific responses. Various routes of carrier entry into skin include follicular pathway, normal pores present in the skin, lamellar lipid bodies and through corneocytes. Among various approaches for non-invasive immunization, i.e. Physical approaches, chemical approaches and vesicular approaches, are gaining wide acceptance for topical vaccination and for attaining sustained delivery of a drug. Another major concern is the regulatory issues of transdermal products to be launched in the market. This review deals with a brief insight on the physiological properties of the skin, several techniques for drug permeation enhancement and regulatory issues over transdermal drug delivery and most of the new active transport technologies involved in enhancing the transdermal permeation into an effective DDS. In-depth analysis, formulation approaches, applications is discussed.
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