N G Turner1, Y N Kalia, R H Guy. 1. Department of Biopharmaceutical Sciences, University of California-San Francisco 94143-0446, USA.
Abstract
PURPOSE: The objective of this study was to determine the extent to which current passage perturbed the skin's intrinsic permeability, and to quantify how quickly and to what extent the barrier properties recovered from the effects of iontophoresis. METHODS: Laser scanning confocal microscopy (LSCM) and impedance spectroscopy (IS) were employed, respectively, to visualize and quantify the recovery kinetics. RESULTS: LSCM images were obtained following passive calcein diffusion through pre-iontophoresed HMS skin in vivo that had been allowed to recover for progressively longer periods of time. IS was used to quantify the rate and extent of skin permeability recovery following current pretreatment. Impedance spectra were recorded 0, 3, 5, 7, 9 and 18 hrs after current termination. CONCLUSIONS: Enhanced calcein permeability as assessed by confocal microscopy persisted for up to 24 hrs following current passage. Consistent with these LSCM findings, IS indicated that the time required for the impedance of hairless mouse skin to return to pre-iontophoresis levels (following 2-hr current passage at 0.5 mA/cm2) was at least 18 hrs.
PURPOSE: The objective of this study was to determine the extent to which current passage perturbed the skin's intrinsic permeability, and to quantify how quickly and to what extent the barrier properties recovered from the effects of iontophoresis. METHODS: Laser scanning confocal microscopy (LSCM) and impedance spectroscopy (IS) were employed, respectively, to visualize and quantify the recovery kinetics. RESULTS: LSCM images were obtained following passive calcein diffusion through pre-iontophoresed HMS skin in vivo that had been allowed to recover for progressively longer periods of time. IS was used to quantify the rate and extent of skin permeability recovery following current pretreatment. Impedance spectra were recorded 0, 3, 5, 7, 9 and 18 hrs after current termination. CONCLUSIONS: Enhanced calcein permeability as assessed by confocal microscopy persisted for up to 24 hrs following current passage. Consistent with these LSCM findings, IS indicated that the time required for the impedance of hairless mouse skin to return to pre-iontophoresis levels (following 2-hr current passage at 0.5 mA/cm2) was at least 18 hrs.