IONTOPHORETIC ENHANCEMENT OF PEPTIDES - BEHAVIOR OF LEUPROLIDE VERSUS MODEL PERMEANTS

In this study the iontophoretic enhancement of transdermal transport of leuprolide in vitro was examined. The behaviour of leuprolide flux enhancement 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 human skin. The results presented here support the following hypothesis: leuprolide 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 electroosmotic flow implies that the convective solvent flow would impede rather than assist the flux of a positively charged permeant and assist the iontophoretic flux of negatively charged permeants.