Pre-treatment with chemical penetration enhancers in dermal/transdermal drug delivery

Delivery of drugs through skin is an alternative route of drug administration. However dermal/transdermal delivery of drugs is limited by the exceptional barrier function of the stratum corneum which forms the outermost layer of the skin. Various active and passive techniques have been successfully employed to breach this barrier function thereby allowing permeation of therapeutic levels of drug across and into the skin. One such approach has been the use of chemical penetration enhancers (CPEs). CPEs are often incorporated in the semisolid formulations and patches intended for application on the skin. Often, incorporation of CPEs in the formulation is limited by their potential for interaction with the API and other excipients in the formulation. Moreover, prolonged contact of CPEs increases the risk of significant damage to the skin structure as well as could potentially lead to skin reactions. Pre-treatment of the skin with these CPEs allows for a reversible modulation of the stratum corneum harrier without getting in contact with the formulation. This avoids any possible incompatibility and instability issues. Thus, pre-treating the skin with CPEs followed by application of drug formulation can be considered as a practical alternative to achieve enhancement into and across the skin.