Model systems in iontophoresis — transport efficacy

Experimental model systems used to study the transport efficacy of ionic compounds through skin during iontophoresis are reviewed. Emphasis has been placed on the ability of these model systems to predict transport efficacy in vivo. Comparative studies using these model systems show that systems based on excised skin can significantly underestimate drug flux achievable in vivo under identical formulation and electrical conditions and that the isolated perfused porcine skin flap model accurately predicts in vivo drug flux. Using the hypothetical example of the drug Dilaudid™ in an iontophoretic device for the non-invasive management of pain, the differences in transport efficacy determined with an excised skin model and the skin flap model are shown to significantly impact the estimation of the commercial viability of the device.