Effects of application voltage and cathode and anode positions at electroporation on the in vitro permeation of benzoic acid through hairless rat skin

The enhancing effect of electroporation on the in vitro skin permeation of benzoate was evaluated. Needle and ring electrodes made of Ag/AgCl were con nected to an electrical power source, which produced exponentially decaying pulses, The needle electrode was kept in contact with the skin surface, an d the ring electrode was positioned either on or under the skin. The electr ical pulse was applied to abdominal hairless rat skin at 150-600 V every mi nute from 3 to 6 h during the 10-h permeation experiment. Skin permeation o f benzoate was promoted by electroporation and the effect was increased by application of a higher voltage. No immediate recovery to the control flux, however, was observed for high voltage groups after turning off the voltag e application. When the cathode and anode were separated by the skin membra ne by setting in the epidermal and dermal sides, respectively, an iontophor etic effect may also play a role in benzoate flux. These results indicated that the drug permeation by electroporation is the result of passive diffus ion and an iontophoretic effect as well as the electroporation effect.