AC iontophoresis studies can also provide insights into
the transport pathways of the stratum corneum (SC) in
passive transport and during iontophoresis. For example, the
effective length of the transport pathway in SC can be
determined by model analyses of transport data during AC.
The intrinsic barrier properties of HEM can be studied using
AC iontophoresis of voltage below the threshold of electric
field-induced HEM alteration (17). The iontophoretic pathways
of AC-altered HEM can be investigated using AC
iontophoresis of higher voltage. It was previously hypothesized
that there exists different transport pathways for ionic
and neutral permeants (3) and for neutral permeants under
the low and high AC voltage conditions in HEM (18).
AC iontophoresis can provide an excellent opportunity to
characterize the effective length of the iontophoretic transport
pathways in SC which would be difficult to achieve in
other experimental settings. Such assessment of the iontophoretic
transport pathways in HEM can be accomplished by
the methodology established in the previous study (3).