Variable-influence pathways, characterization

When an electric potential is imposed across the skin, as in iontophoresis, ions will move along the pathways of lowest electrical resistance. Although the exact anatomical location of these low-resistance shunt pathways has not been well characterized, recent microscopy studies have shed mechanistic insight on the problem. Experimental variables of particular importance that have been shown to strongly influence the preferred iontophoretic transport pathways include (a) the physicochemical nature of the penetrant and (b) the penetrant s affinity for the different environments available (e.g., hair follicle, sweat duct, intercellular lipids). These unresolved and, in some cases, controversial issues will be discussed in the context of both classical and recent microscopy investigations. 

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