Examination of Iontophoretic Transport of Ionic Drugs Across Skin. 1. Baseline Studies with the Four-Electrode System.

Recently there has been increased interest in the possibility of utilizing iontophoresis for drug transport across skin. Although previous studies with conventional two electrode systems have shown that it is feasible to obtain flux enhancement of drugs across membranes by iontophoresis, they have not provided data relating the actual potential drop across a membrane with the iontophoretic flux. The principal difficulty with the two-electrode system is that it does not permit the direct determination of the potential drop across the membrane. The purpose of the present communication is to examine the validity of an equation derived from the NernstPlanck relationship describing flux enhancement of charged molecules across a membrane or skin caused by an electric field. In order to test this equation with experimental data, a four electrode system for a two chamber diffusion cell assembly was developed which allows for the first time determination and control of the actual potential drop across a membrane.