Transdermal delivery penetration routes

Drugs chosen for delivery via a transdermal drug-delivery system must adequately penetrate the skin in such a way that the system determines the delivery rate that should be fairly constant. In addition, the drug must not irritate or sensitize the skin. It is hoped that in the future more drugs will be developed for transdermal delivery. This could become an alternative route for drug delivery to children who have difficulty with oral administration. 

The chitosan and its derivatives show no acute toxicity and are not absorbed via transdermal route. The European pharmacopoeia contains a single monograph on chitosan hydrochloride. In the United States, chitosan is currently being included in the US Pharmacopoeia [Sarmento and das Neves, 2012]. The chitosan and its derivatives are deemed safe for use as permeation enhancer for transmucosal delivery of hydrophilic drugs and offer promising prospects for novel pharmaceutical applications [Junginger and Verhoef, 1998]. Despite the chitosan and its derivatives interact with lipids and proteins of the membranes of stratum corneum, they may not penetrate into deeper layers of the skin. This can be inferred from the absence of skin irritation by chitosan and its derivatives in Draize test [Aoyagi et al., 1991]. 

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