Pharmaceutical drugs and formulations suitable for iontophoresis thereof that provide enhanced iontophoretic delivery of an anti-fungal drug to at least one body surface, such as a nail, are described. Also described are pharmaceutical formulations suitable for iontophoresis comprising terbinafine and methods for administering terbinafine to a body surface via iontophoresis. When the drug source is introduced into the nail using a mask, terbinafine concentrations in peripheral areas of nail following iontophoretic treatment are less than drug concentrations directly under the mask. Further, differences in delivered drug concentrations is effectuated by creating drug delivery gradients. Drug can be delivered to dissimilar tissues based on different transfer efficiencies exhibited by the dissimilar tissues, resulting in higher percentage delivery in one tissue vs. another tissue.