Microspheres of copolymeric N-vinylpyrrolidone and 2-ethoxyethyl methacrylate for the controlled release of nifedipine

Free radical copolymerization of N-vinyl-2-pyrrolidone (NVP) with 2-ethoxyethyl methacrylate (EOEMA) was carried out with 2,2'Œ- azobisisobutyronitrile (AIBN) initiator in 1,4-dioxane solvent at 60 °C. The resulting copolymers were characterized by FTIR, 1HNMR and 13C-NMR methods. Microspheres were prepared by varying the amount of NVP with respect to EOEMA. Nifedipine (NFD), a water-insoluble antihypertensive drug, was loaded into these microspheres by the oil in water emulsion technique followed by solvent evaporation. The effect of the proportion of NVP in the NVP/EOEMA copolymer on the controlled release of NFD from the microsphere matrix was investigated. Scanning electron micrographs (SEM) of the microspheres indicated spherical shapes in the size range 17.47 μm, even after loading with NFD. In vitro studies of the release of NFD from the NVP/EOEMA microspheres in pH 7.4 medium showed that the rate of NFD release was enhanced when the NVP content of the copolymer was high; the size of the microspheres also increased with increasing NVP content of the copolymer. Release data were analyzed using an empirical relation in order to elucidate the kinetics of the NFD release. This analysis indicated that a Fickian transport mode operates in this system.