The effect of controlled osmotic stress on release and swelling propertiesof a water-in-oil emulsion

The purpose of this study was to investigate the effect of osmotic gradient s in a water-in-oil (w/o) emulsion on release properties in order to contro l the release of hydrophilic drugs. The magnitude and direction of the osmo tic gradient was shown to have a pronounced effect on the apparent permeabi lity of the hydrophilic marker, [H-3]glucose. The apparent permeability coe fficient of glucose could be varied between 1.0 x 10(-8) and 5.0 x 10(-8) c m s (-1) using osmotic gradients. The release rate of glucose was related t o the swelling properties. The larger the degree of swelling, the lower the release rate. Furthermore the present w/o emulsion has a low viscosity and a long-term physical stability. This makes the emulsion a promising parent eral drug delivery system in which the release of hydrophilic drugs such as peptides, can be controlled. (C) 1999 Elsevier Science B.V. All rights res erved.