IONTOPHORETIC ENHANCEMENT OF PEPTIDES - BEHAVIOR OF LEUPROLIDE VERSUSMODEL PERMEANTS

In this study the iontophoretic enhancement of transdermal transport o f leuprolide in vitro was examined. The behaviour of leuprolide flux e nhancement was inconsistent with earlier obtained results with a small positively charged compound. Therefore, a thorough investigation was undertaken to discover the mechanisms of the inconsistent behaviour of this positively charged peptide, using both a model membrane and huma n skin. The results presented here support the following hypothesis: l euprolide adsorbs an to the negatively charged membrane, leading to a change in the net membrane charge and therefore changing the direction of the electroosmotic flow. A reversal of the direction of the electr oosmotic flow implies that the convective solvent flow would impede ra ther than assist the flux of a positively charged permeant and assist the iontophoretic flux of negatively charged permeants.