EFFECT OF DRUG CONCENTRATION IN THE MONOMER CROSS-LINKER MIXTURE ON THE LOADING LEVELS AND THE RELEASE KINETICS OF NONSTEROIDAL ANTIINFLAMMATORY DRUGS FROM ETHYLENE-GLYCOL DIMETHACRYLATE CROSS-LINKED POLYHYDROXYETHYL METHACRYLATE MICROSPHERES

This study assesses the loading process of ethylene glycol dimethacryl ate cross-linked poly (2-hydroxyethyl methacrylate) microspheres by in corporation of non-steroidal anti-inflammatory drugs in the monomer/cr oss-linker mixture before polymerization. The authors studied the effe ct of the active principle concentration in the mixture on loading lev els, swelling times and release kinetics of the microspheres. The load ing efficiency is higher at drug concentrations in the mixture lower t han its saturation value. The release kinetics approaches zero order b oth during and after swelling. The diffusional exponents are higher du ring than after swelling.