AN ANALYSIS OF DRUG AND SOLUTE TRANSPORT THROUGH MEMBRANES BASED ON POTENTIAL BARRIERS

Modelling of drug or solute transport in membranes including those used in transdermal systems is often based on Fickian diffusion analysis. Such transport requires knowledge of the size exclusion characteristics and the membrane reflection coefficient as functions of the physiological conditions of the system. We offer a modified analysis with which one can calculate drug reflection coefficients in polymer membranes used in transdermal delivery. In our analysis, the solute molecule is visualized as traveling across successive potential barriers created by steric effects, electrostatic interactions or other forces from charged or uncharged molecules. The membrane is assumed to present only one potential barrier since the random network need not possess any anisotropy. A two-dimensional network with vanishing thickness allows the approximation of one-directional transport. The result is the formulation of a potential barrier model that can be used to analyze various solute transport situations. Various experimental results from our laboratory and other investigators are analyzed using this theory. For the time being the theoretical model applies to relatively low molecular weight solutes.