Electric field analysis on the improved skin concentration of benzoate by electroporation

The objective in the present study was to understand the relationship betwe en the increased skin concentration of benzoate as a model drug after topic al application of its sodium salt and the electric field intensity produced in the skin barrier, the stratum corneum, by electroporation. A piece of e xcised abdominal hairless rat skin was set in a Franz type diffusion cell, and 0.5% sodium benzoate and physiological saline were applied to the strat um corneum and dermis sides, respectively. Two needle electrodes made of Ag were connected to an electrical power sourer, which produced exponentially decaying pulses. The electrodes were placed on the skin surface with a dis tance of 0.5 cm between both electrodes. After the 4 h passive permeation e xperiment, an electrical pulse was applied to the rat skin at 300 V every m inute for 10 min. The skin was then removed from the diffusion cell, and th e amounts of benzoate in different positions of the skin specimen were meas ured. Field intensity generated in the stratum corneum by electroporation w as determined by a finite element method using a computer program. The amou nts of benzoate at different sites in the skin were almost proportional to the mean field intensity in the corresponding stratum corneum. These result s suggested that the enhancing effect of electroporation can be evaluated b y the field intensity more directly than the application voltage. (C) 2001 Elsevier Science B.V. All rights reserved.