DISSOLUTION MEDIUM INDEPENDENT RELEASE OF PROPRANOLOL FROM SILICONE RESERVOIR DEVICES

The effect of aqueous dissolution medium properties on the release of model drug, propranolol, from water-activated and pH-controlled device s was investigated in vitro in diffusion cells. In the devices, powder s of propranolol hydrochloride and pH-adjusting adjuvant, disodium pho sphate, were entrapped between two silicone membranes. pH of dissoluti on medium ranged from 1.6 to 9.4, osmotic pressure from 138 to 950 mOs m/kg and ionic strength was 0.15 or 0.3. The osmolality and ionic stre ngth of dissolution medium affected neither the inner pH and water con tent in the device nor the release of propranolol from the devices. Wh en pH in the dissolution medium was raised, the inner pH of the device was increased slightly but not adequately to change propranolol relea se. Thus, the release of propranolol from the tested silicone reservoi r devices was essentially independent of its environment.