TRANSDERMAL TRANSPORT EFFICIENCY DURING SKIN ELECTROPORATION AND IONTOPHORESIS

High-voltage pulsing has previously been shown to dramatically increas e molecular transport across skin. The goal of this study was to exami ne the functional dependence of transdermal transport on pulse paramet ers and to make comparisons with iontophoresis. Transdermal transport of calcein, a model drug, was measured during low-voltage, constant el ectric fields (iontophoresis) and high-voltage pulsed electric fields (hypothesized to cause electroporation). In the first part of the stud y, the dependence of calcein flux caused by high-voltage pulses was de termined as a function of pulse length, rate, polarity, waveform, and total pulsing time. In the second part, calcein transport numbers were calculated for both iontophoresis and high-voltage pulsing, and expre ssed as functions of pulse parameters. For both iontophoresis and high -voltage pulsing. transport numbers (or transport efficiency) ranged f rom 10(-5) to 10(-2) and were functions of voltage and current, but di d not show dependence on pulse length, rate, energy, waveform, or tota l charge transferred. The resulting estimates of the area fraction of skin available to transport were larger during high-voltage pulsing (1 0(-3) for small ions and 10(-6) to 10(-3) for calcein) than during ion tophoresis (10(-5) to 10(-4) for small ions and 10(-8) to 10(-4) for c alcein).