Iontophoretic delivery of drugs through membranes including human stratum corneum

In Vivo ac Impedance Spectroscopy of Human Skin: Theory and Problems in Monitoring of Passive Percutaneous Drug Delivery

“…The value of R p is closely associated with the flow of ionic current and hence with the passive ion permeability of the skin. 1,3 R p is the parameter most often used in transdermal drug delivery to evaluate the effects of hydration, passive diffusion, and iontophoresis on the skin. When comparing the R p values of hydrated skin and iontophoresed skin, it was found that the iontophoresed skin had much lower R p values, indicating that iontophoretically induced charge had increased the permeability of skin to passive ion transport.…”

“…When comparing the R p values of hydrated skin and iontophoresed skin, it was found that the iontophoresed skin had much lower R p values, indicating that iontophoretically induced charge had increased the permeability of skin to passive ion transport. 1,3 R p depends on inter‐ and intrahuman variabilities such as the presence and activity of sweat glands. 10 It depends further on psychological events; on the thickness, permeability, and integrity of the epidermis; on the electrode application time; and on the composition of the electrode gel, drug, or bathing solution.…”

“…The capacitance of the skin appears to reflect the condition of the stratum corneum. For example, although Foley et al 3 found that the skin's capacitance was not significantly affected during drug delivery through the stratum corneum, they reported however that the use of penetration enhancers or the application of high current densities (during iontophoretic delivery) altered the skin's capacitance, indicating changes in the structure of the stratum corneum or its destruction.…”

“…Electrical impedance spectroscopy (EIS) has been recently applied in the field of transdermal drug delivery 1‐8 to monitor the electrical properties of treated skin sites in an effort to monitor changes resulting from transdermal drug diffusion. At present, there is no acceptable method of accurately assessing how much drug has crossed, is crossing, or will cross the skin barrier and of establishing the presence and degree of skin damage occurring under occlusive, drug‐containing patches.…”

Skin Membrane Electrical Impedance Properties under the Influence of a Varying Water Gradient

“…The capacitor (C) has been associated with restriction of ion transfer at low conductive lipid and lipid-protein domains of the SC (8,16,18,19). In the case of in vitro studies on excised skin membranes, representative values of these elements are on the order of R sol~2 00 Ohm cm 2 , R mem~1 0-200 kOhm cm 2 , and C~10-50 nF cm À2 (7,8,20).…”