HYDROPHILIC MODEL-DRUG DELIVERY FROM CONCENTRATED REVERSE EMULSIONS

Highly concentrated water-in-oil gel-emulsions have been prepared from five components: fluorocarbon, hydrocarbon, fluorinated and hydrogena ted surfactants, and water. Whatever the ratio of fluorinated to hydro genated compounds, the stability of these mixed emulsions allows them to be used for the transport of drugs. A series of model molecules sol ubilized in water have been chosen because of the modulation of the hy drophobicity of the probe molecule by varying the alkyl substitute len gth: methyl, ethyl, and propylparaben. The release of these molecules has been studied with an automatic setup. The experiments take about 4 8 h to reach equilibrium regardless of the emulsion composition. Never theless some variations have been observed with respect to either the chosen probe molecule or the amount of hydrogenated and fluorinated co mpounds in the gel emulsion. In light of the results, diffusion takes place in two possible steps: (i) transfer from big droplets to the con tinuous micellar phase and (ii) transfer from the continuous oily phas e to the aqueous receptor solution. The influence of these two steps i s related to the molecular structure of the model drug on one hand and to its solubility both in the micellar oily phase and in the aqueous phase constituting the gel emulsion in the other hand.