ABSTRACT
Transdermal drug delivery is an emerging eld with key applications in local delivery of molecules to local tissue sites, through to systemic delivery applications under sustained-release conditions. Historically, transdermal delivery has been limited to molecules that t a narrow physicochemical prole (low molecular weight, adequate solubility in both oil and water, high partition coef- cient); however, the range of deliverable drugs is rapidly expanding on all fronts, thanks to advances primarily in (1) enhancing the permeability of the outermost skin layer (stratum corneum [SC]), (2) increasing the driving force for drug transport across the SC, (3) physical approaches that bypass the SC altogether, and (4) novel combinations of these methods. With ≈20 small molecule drug delivery systems (DDS) currently FDA-approved involving transdermal approaches, based on current trials in small animals and humans, it is likely that delivery of genetic and cellular therapies, vaccines, therapeutic proteins, and nanoparticle-encapsulated systems will be available in the near future.
