Abstract
Drug delivery systems on a polyurethane base with various antitumorous drugs, such as cyclophosphane, thiophosphamide and vincristine, have been prepared. An in vitro technique was used to determine the release characteristics of the drugs into model biological media. It was shown the drug release occurs in accordance with first-order kinetics, as well a maximum degree for the drug loading were studied. The thermodynamic parameters of drug release has been determined. It was illustrated that the activation energies were 4.3, 3.9 and 3.2 kcal/mole for cyclophosphane, thiophosphamide and vincristine respectively, corresponding to a diffuse-controlled mechanism of release. © 1998 John Wiley & Sons, Ltd.