Preparation and evaluation of multiple emulsions as controlled release topical drug delivery systems

In the present investigation the use of multiple emulsions as controlled release topical drug delivery systems was evaluated. Sodium salicylate and methyl salicylate which vary in their lipid solubility were selected for the study. The Franz diffusion cell system and cellulose membrane were used for all in vitro release studies.;The release rate of sodium salicylate from multiple emulsions was slower than from the corresponding aqueous solutions containing polymers. The multiple emulsions prepared using Avicel RC-591 released the drug faster than the multiple emulsions containing xanthan gum.;The multiple emulsions prepared by using Carbopol 1342 as the secondary emulsifier showed the average release rates and effective diffusion coefficients decreased significantly (p ;A prolongation of 73% of drug release was obtained by adding sodium chloride to the internal aqueous phase. However, the addition of glycerin in the internal aqueous phase did not control the release of the drug.;Water-in-Oil-in-Water (W/O/W) Emulsion Systems: The physical stability of sodium salicylate w/o/w multiple emulsions was found to be stable for 2 months at room temperature. These multiple emulsions exhibited non-Newtonian flow, specifically pseudoplastic behavior, on increasing shear rate. The viscosity and droplet size of multiple emulsions were strongly influenced by storage temperature and aging.;Oil-in-Water-in-Oil (O/W/O) Emulsion Systems: The physical stability of methyl salicylate o/w/o multiple emulsions indicated rapid coalescence of internal oil droplet and breaking down of multiple emulsion droplets.;The multiple emulsions prepared by using Carbopol 1342 as a primary hydrophilic emulsifier showed that average drug release rate and effective diffusion coefficients decreased significantly (p ;No systemic absorption of sodium salicylate and methyl salicylate was observed from topical application of multiple emulsions in guinea pigs.;The multiple emulsion formulations developed are believed to have potential for use as controlled release topical drug delivery systems.