INFLUENCE OF LIPOPHILIC SURFACTANT ON THE RELEASE KINETICS OF WATER-SOLUBLE MOLECULES ENTRAPPED IN A W O/W MULTIPLE EMULSION/

The aim of this work was to study the release kinetics of a water-solu ble drug from two different W/O/W multiple emulsions prepared with two lipophilic surfactants at different concentrations. The study of the kinetics under both iso-osmotic and hypo-osmotic conditions allowed us to distinguish between two possible release mechanisms: swelling-brea kdown or facilitated diffusion. The results obtained indicate that wat er-soluble drug release occurs by a mechanism of swelling followed by a breakdown of the oil globules, in which the lipophilic surfactant is a decisive factor. It appears that the globule's swelling capacity is considerably increased when the lipophilic surfactant concentration i ncreases, and the more the oil globule swells, the less the water-solu ble drug releases. It seems that the stability could be improved by in creasing the lipophilic surfactant concentration which could strengthe n the interfacial film. In contrast, an excess of hydrophilic surfacta nt destabilized the emulsion.