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 dimethacrylate cross-linked poly (2-hydroxyethyl methacrylate) microspheres by incorporation of non-steroidal anti-inflammatory drugs in the monomer/cross-linker mixture before polymerization. The authors studied the effect of the active principle concentration in the mixture on loading levels, swelling times and release kinetics of the microspheres. The loading efficiency is higher at drug concentrations in the mixture lower than its saturation value. The release kinetics approaches zero order both during and after swelling. The diffusional exponents are higher during than after swelling.