Novel penetration enhancers for skin applications: a review

The use of topical formulation is popular over the past decade due to extensive researches made in the field of transdermal drug delivery. As a result, an increasing number of drugs are being added to the list of therapeutic agents that can be delivered to systemic circulation through the skin. Commonly available dosage forms for the topical application are creams, ointments, gels, patches etc. The therapeutic benefits of the above topical formulations are limited due to barrier property of stratum corneum (SC). The use of chemical penetration enhancers (CPEs) is one of the long standing approach to overcome the barrier property of SC. Numerous class of novel compounds have been evaluated for penetration enhancement activity, including soft enhancement for percutaneous absorption (SEPA), for example, 2 N-nonyl-1,3- dioxolanes, N-acetyle prolinate esters (such as pentyl- and octyl-N-acetyle prolinate), alkyldiloxanes (e.g., 1-Alkyl-3-b-D glucopyranosyl-1,1,3,3-tetramethyl disiloxanes), transcarbam (such as 5-(dodecyloxycarbonyl) pentylammonium-5- (dodecyloxycarbonyl) pentylcarbamate), iminosulfurane (like N-hexyl,N-benzoyl-S,S-dimethylimino-sulfuranes), capsaicin derivatives (e.g., Nonivamide), cinnamene compounds (such as cinnamic acid, cinnamaldehyde etc), terpenes (like clove and basil oil) and synergestic combination of penetration enhancers (SCOPE). We briefly describe about the anatomy of skin. Potential mechanisms of action of above novel PEs along with adverse reactions associated with traditional PEs are also considered in this review.