Abstract

Roshani Sadafale*

ABSTRACT

Physicochemical properties of the human nail plate exhibit a marked difference to that of epidermis, resulting in very different permeability characteristics. Whereas the SC behaves as a lipid barrier to the permeation of low MW chemicals, the nail plate exhibits behaviors similar to that of a hydrogel with high ionic strength and, indeed, the structure of human nail has been likened to a hydrophilic gel membrane. The lipid content of the nail is reported to be low, at between 0.1– 1%, and the nail is much more susceptible to water loss than the lipid-rich skin. Despite the reported hydrophilic properties of the nail, hydrophobic compounds also have been shown to diffuse into and through this barrier. For example, Walters and coworkers reported that long chain alcohols also permeate through the nail via a lipidic pathway. For effective transungual drug therapy, permeation must be enhanced. This can be achieved by disrupting the nail plate using physical techniques or chemical agents. Alternatively, drug permeation into the intact nail plate may be encouraged, for example, by iontophoresis or by formulating the drug within a vehicle which enables high drug partition out of the vehicle and into the nail plate. There are several physical techniques that have been shown to enhance transungual delivery.