Recovery of skin barrier properties after sonication in human subjects

The SonoPrep(R) ultrasonic skin permeation system is used clinically to increase skin permeability for rapid, noninvasive delivery of local anaesthetics. This study tested the hypothesis that sonication can generate a long-lived increase of skin permeability for continuous transdermal drug delivery and diagnostic metabolite extraction. To accomplish this, the volar forearm skin of ten healthy adult subjects was sonicated. As a surrogate measure of skin permeability, skin electrical impedance was measured at occluded and nonoccluded sites every hour over a period of 48 h. Sonication dramatically increased skin permeability, as demonstrated by a large drop in skin impedance. Under occlusion, sonicated skin remained highly permeable during the entire 42-h period of occlusion, which was followed by an immediate decrease in permeability upon removal of occlusion. Without occlusion, sonicated skin retained elevated permeability throughout the 48-h experiment, but regained its barrier function more quickly. Therefore, sonication can increase skin permeability for prolonged periods of time, especially under the effect of occlusion, and has potential to facilitate continuous transdermal drug delivery and diagnostic metabolite extraction.