ABSTRACT
Skin is an optimal interface for systemic drug administration. Transdermal drug delivery (TDD) is the controlled release of drugs through intact and/or altered skin to obtain therapeutic levels systematically and to affect specied targets for the purpose of, for example, blood pressure control, pain management, and others. Dermal drug delivery (DDD) is similar to TDD except that the specied target is the skin itself [1]. TDD has the advantages of bypassing gastrointestinal incompatibility and hepatic “rst pass” effect; reduction of side effects due to the optimization of the blood concentration time prole; predictable and extended duration of activity; patient-activated/patient-modulated delivery; elimination of multiple dosing schedules, thus enhancing patient compliance; minimization of interpatient and intrapatient variability; reversibility of drug delivery allowing the removal of drug source; and relatively large area of application compared with the mucosal surfaces [1]. After nearly four decades of extensive study, the success of this technology remains limited, with many problems waiting to be solved, one of which is the challenge of low skin permeability hindering the development of TDD for macromolecules. To overcome the skin barrier safely and reversibly while enabling the penetration of macromolecules is a fundamental problem in the eld of TDD and DDD.
