‘Dry emulsion’ — a sustained release form: Modelling of drug transfers in liquids

A galenic form made of a dry emulsion was described and tested by considering the drug release in synthetic liquids. It was obtained by mixing the two following phases: the one with water, sodium salicylate as drug and hydrophilic silica in powder form; the other being a lipidic phase with oil and hydrophobic silica. A model, based on a numerical method with finite differences, was applied to the case of spherical samples. The theoretical results for the kinetics of drug release were in good agreement with the corresponding experimental ones. Dry emulsion exhibited a significant sustained drug release, controlled by diffusion with a constant diffusivity and a coefficient of matter transfer characterizing the retardation in the transfer on the surface.