CROSS-LINKED POLY(ETHYLENE OXIDE) FOR DRUG-RELEASE SYSTEMS

Three types of poly(ethylene oxide)(PEO)- based hydrogels have been sy nthesized and studied for drug release applications: gamma-irradiated high molecular weight PEO, biodegradable polyether-polyester networks with malic acid as crosslinker of poly(ethylene glycol)s and amphiphil ic PEG-based polyureas crosslinked with multifunctional isocyanates. V arying the length of the PEO chain and the type of the crosslinker, hy drogels with different swelling properties, loading capacities and rel ease characteristics were obtained. A large number of pharmaceuticals (acebutolol.HCl, diclofenac.Na, procaine.HCl, phenobarbital.Na, propra nolol, etc.) were tested for a sustained release in different media (p H=1.2, 6.5, 7.4). Most of them gave reasonable retarded release profil es for 8 hours when incorporated before the gamma-irradiation crosslin king of PEO. While amphiphilic hydrogels were found to be suitable for hydrophobic solutes, the biodegradable PEG-based polyester ones affec ted predominantly the release of water-soluble drugs. No pH effect was found for the gamma-irradiated PEO as a carrier in contrast to the st rong pH dependence for the degradable polyester networks.