Penetration enhancers for TDDS: A tale of the under skin travelers

The noninvasive route of delivery systems has many advantages over the conventional delivery systems. Although its applications are limited by low skin permeability and physicochemical properties of drugs The permeation of drugs through skin can be enhanced by various methods including phys ical methods such as iontophoresis (application of low level electric current), phonophoresis (use of ultra sound energy), eletroporation and by chemical penetration enhancers etc. The transdermal route has been recognized as one of the highly potential routes of systemic drug delivery and provides the advantage of avoidance of the first-pass effect, ease of use and withdrawal (in case of side effects), and better patient compliance. However, the major limitation of this route is the difficulty of permeation of drug through the skin. Studies have been carried out to find safe and suitable permeation enhancers to promote the percutaneous absorption of a number of drugs. The present review highlights various categories of penetration enhancers; the involved mechanism leading to a judicious s election of suitable penetration enhancers for improving the transdermal permeation of poorly absorbed drugs.