Transdermal iontophoretic permeation of luteinizing hormone releasing hormone: Characterization of electric parameters

A single-compartment iontophoretic permeation cell incorporated with two polyacrylamide hydrogel reservoir devices was used to characterize the effect of several electrical parameters on transdermal iontophoretic permeation of LHRH through hairless rat skin. Receptor solutions and skin regions were selected before evaluating the effect of electrical parameters, which included different application patterns, various waveforms and on/off ratios. Iontophoretic permeation of LHRH was higher while current was applied continuously rather than in an intermediate pattern. The difference among various waveforms was not significant. However, triangular wave seems to have the least iontophoresis enhancing effect and different voltage profiles. The on/off ratios of pulsed direct current showed a significant effect on transdermal iontophoretic permeation of LHRH, and demonstrated that the higher the on/off ratio (duty cycle), the greater the skin permeation of LHRH. Duration of current application was more important than amplitude and intensity of current in terms of transdermal iontophoresis. The voltage profiles (including onset, apparent and offset voltage) for different on/off ratio with either same or different current amplitude demonstrated that the voltage reduction was very slow for the on/off ratio with a lower value. This implies that the skin resistance remained high during current application resulting in lower skin permeation of LHRH for lower on/off ratio.