Skin Absorption Modulation: Innovative Non-Hazardous Technologies for Topical Formulations

The achievement of skin drug delivery needs to conciliate two paradoxical terms: firstly, the major barrier of permeation formed by the stratum corneum needs to be circumvented for skin drug delivery (i.e., skin absorption); secondly, the drug deposition within the skin should be ideally accomplished with a restricted percutaneous absorption. At strictly speaking, the terms of this paradox are not solvable, since Fick's laws stipulate that the rate of drug transport is not separable from the gradient of drug concentration. In this field, drug carriers as vehicle have been reported in the recent years as one of the most promising strategy to address skin drug delivery. Indeed, the passage of drug loaded particles through the stratum corneum and/or via the follicular ducts might (i) target the drug deposition in specific skin sites, (ii) control and sustain the cutaneous drug release, (iii) protect the drugs against substantial epidermal metabolism, and (iv) reduce the percutaneous absorption. The present paper reviews the different drug carrier systems which do not require solvent in their process, with their physicochemical characteristics, the mechanisms of drug delivery and drugs that were efficiently used as a penetrant.