Transfer of diclofenac sodium across excised guinea pig skin on high-frequency pulse iontophoresis. I. Equivalent circuit model.

High frequency pulse iontophoresis of diclofenac sodium across excised guinea-pig skin was carried out in vitro. An equivalent circuit model was constructed to simulate the time courses of voltage drop across the donor solution and the skin. Parameter values obtained by the least-squares adaptation of the model to observed data were consistent with expectation and validated the proposed model.

Transfer of diclofenac sodium across excised guinea pig skin on high-frequency pulse iontophoresis. II. Factors affecting steady-state transport rate.

Some of the factors affecting the steady-state transport rate of diclofenac sodium across excised guinea-pig skin during high-frequency pulse iontophoresis were examined. The same mathematical expression was employed for enhancement ratio as a function of applied voltage as the one derived for direct-current iontophoresis. The effective voltage drop across the skin was only 1.1% of the applied voltage. The steady-state flux value increased with increase of the donor concentration.

[Enhanced percutaneous absorption of formoterol furmarate via pulsed iontophoresis. I. Effect of constant current and constant voltage].

The effect of iontophoresis on percutaneous absorption of formoterol fumarate (FF) was investigated in vitro with abdominal skin excised from guinea pig. By passive diffusion, the flux at steady state for stripped skin was about 230 times greater than that for intact skin. Therefore, it is suggested that stratum corneum is a barrier for the percutaneous absorption of FF. Penetrated amount of FF increased significantly with an increase in donor concentration from 0.035% to 0.07%. Under the constant current iontophoresis the large flux accompanied with the high applied voltage was shown at the beginning of iontophoresis. Thereafter the flux decreased with a decrease in applied voltage. Under the constant voltage iontophoresis a linear relationship between penetrated amount of FF and time was observed.

[Enhanced percutaneous absorption of formoterol fumarate via pulsed iontophoresis. II. Effect of polarity, pulse frequency and duty].

To clarify the effect of polarity, pulse frequency and duty on the iontophoretic transport of formoterol fumarate (FF), in vitro and in vivo studies were performed with guinea pigs. In the in vitro studies, the flux at steady state was enhanced by the factor 7.61 with anodal iontophoresis in comparison with control, whereas, with cathodal iontophoresis it was restrained by the factor 0.79. When pulse frequency was varied from 0 to 40 kHz, the flux at steady state was enhanced with an increase in pulse frequency. In the in vivo studies with varying the duty of pulse potential from 10 to 100%, the maximum plasma concentration of FF was obtained at a 30% duty. In contrast, the plasma concentration of FF achieved at 100% duty was not high. With stripped skin, no significant difference in the plasma concentration of FF was shown between iontophoresis and control. Consequently, it is suggested that iontophoresis contributes to FF penetration across stratum corneum.