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

The purpose of this study was to investigate the effect of osmotic gradients in a water-in-oil (w/o) emulsion on release properties in order to control the release of hydrophilic drugs. The magnitude and direction of the osmotic gradient was shown to have a pronounced effect on the apparent permeability of the hydrophilic marker, [H-3]glucose. The apparent permeability coefficient of glucose could be varied between 1.0 x 10(-8) and 5.0 x 10(-8) cm s (-1) using osmotic gradients. The release rate of glucose was related to 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 parenteral drug delivery system in which the release of hydrophilic drugs such as peptides, can be controlled. (C) 1999 Elsevier Science B.V. All rights reserved.