Drug delivery via ion exchange across a micromembrane.

The exchange of pharmaceutically significant amounts of dopamine across a micromembrane is reported, establishing the practical basis for such a drug delivery system. Drug release was accomplished with a commercially available device initially intended for use as a postcolumn reactor in ion chromatography. Release of other ionic drugs (e.g., methyldopate and piperacillin) was also achieved but with a lesser efficiency than was dopamine, presumably because of a size effect. The effect of releasing ion identification and concentration, the flow rate of the delivery solution and concentration of drug in the device reservoir on the drug release efficiency was examined. Under optimal conditions the efficiency approaches 80%, and 1 mg of drug is released/ml of delivery solution. Alternatively, operating conditions can be changed so that magnitude of release is optimized but absolute efficiency is sacrificed. Under such conditions the magnitude of dopamine release approaches 2 mg/ml but exchange efficiency is approximately 25%.