Transdermal drug delivery enhancement by compounds of natural origin

Abstract

The transdermal route of administration offers an alternative pathway for 20 systemic drug delivery with numerous advantages over conventional routes of 21 administration. Regrettably, the stratum corneum forms a formidable barrier that hinders 22 the percutaneous penetration of most drugs even though it is an important protection 23 mechanism of the organism against entrance of possible dangerous exogenous molecules. 24 Different types of penetration enhancers have shown potential to reversibly overcome this 25 barrier to provide effective delivery of drugs across the skin. Although certain chemical 26 and physical skin penetration enhancers are already employed by the pharmaceutical 27 industry in commercially available transdermal products, some skin penetration enhancers 28 are associated with irritating and toxic effects. This emphasizes the need for the discovery 29 of new, safe and effective skin penetration enhancers. Penetration enhancers from natural 30 origin have become popular as they offer several benefits over their synthetic counterparts 31 such as sustainable mass production from a renewable resource and lower cost depending 32 on the type of extraction used. The aim of this article is to give a comprehensive summary 33 of the results from scientific research conducted on skin penetration enhancers of natural 34 origin. The discussions on these natural penetration enhancers have been organized into the 35 following chemical classes: essential oils, terpenes, fatty acids and polysaccharides.