Transdermal penetrants passive

The remarkable resistance of the SC intercellular lipid network to the passive penetration of therapeutic agents has intensified the search for devices, chemical and physical, with the ability to perturb this lipid environment. Of the many physical techniques investigated, iontophoresis (or electrically enhanced transdermal transport) has become an important focal point [160-162]. Unparalleled in its ability to deliver (noninvasively) ionized drugs across the skin, its modus operandi appears to be largely dependent on transcutaneous ion-conducting pathways (which may be paracellular), rather than a function of direct interaction with the lipid infrastructure [163]. Nevertheless, the effect of the applied current on the lipid (and protein) domains is a matter of interest with respect to both safety considerations (i.e., does the applied current induce stmctural alterations ) and mechanistic insight. ATR-FTIR has been used in a number of studies to discern the effect of iontophoresis on SC lipid and protein structures, both in vivo and in vitro. In separate studies, human SC was examined in vivo following the delivery of current at 0.1-0.2 mA/cm for 30... 

Hirvonen et al. [67] used dodecyl NA -dimethyl amino acetate (DDAA) and Azone as penetration enhancers in the transdermal iontophoresis of sotalol and salicylate. They compared the action of both enhancers in passive diffusion studies and iontophoretic studies and found no significant difference between the two, with the permeability of sotalol in the passive diffusion studies increasing to the order of magnitude found in the iontophoretic studies. The main mechanism of action of DDAA and Azone is the disordering of the lipids and the closing of iontophoretic penetration routes [123,124]. 

Brady, A.B. Corish, J. Corrigan, 0.1. Passive and electrically assisted transdermal delivery of desamino-8-D-argi-nine vasopressin in vitro from a gel matrix. In Prediction of Percutaneous Penetration, Scott, R.C., Guy, R.H., Hadgraft, J., Bodde, H.E., Eds. STS Publishing Cardiff,, U.K., 1991 2, 401-409. 

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