Transdermal enhancement effects of electroporation applied only on the stratum corneum by two electrode types, the stamp-type electrode and the frog-type electrode, were investigated in vitro using excised rat skin. Carboxyfluorescein (CF) was selected as a model compound. The excised skin was set in a Franz type diffusion cell and a square wave electric pulse was applied to the stratum corneum under various electric pulse conditions. We determined the permeability of CF to the receptor compartment under these conditions. Voltage, electric pulse length, and number of electric pulses, were varied from 10 to 1000 V, 50 micros to 15 ms and 5 to 30 pulses, respectively. Flux rate was enhanced as the electric pulse condition strengthened. However, the maximum value was attained in the flux rate, above which no increase was observed despite strengthening of the electric pulse. Although at low electric pulses, the enhancement effect of the frog-type electrode was superior to that of the stamp-type electrode, the maximum flux rates were the same. These results indicate that electroporation on the stratum corneum using the stamp-type electrode or frog-type electrode, is useful for transdermal drug delivery.

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