A NOVEL SKELETAL DRUG-DELIVERY SYSTEM USING SELF-SETTING BIOACTIVE GLASS BONE-CEMENT .3. THE IN-VITRO DRUG-RELEASE FROM BONE-CEMENT CONTAINING INDOMETHACIN AND ITS PHYSICOCHEMICAL PROPERTIES

A novel device containing indomethacin as a model drug using a self-setting bioactive cement based on CaO-SiO2-P2O5 glass was investigated. Glass powders containing 2% and 5% indomethacin hardened within 5 min after mixing with a phosphate buffer. After setting, in-vitro drug release from homogeneous or heterogeneous drug-loaded cement pellets in a simulated body fluid (SBF) at pH 7.25 and 37 degrees C continued for more than 2 weeks. The hardened cement gradually formed low-crystallinity hydroxyapatite and shrunk by about 5% in volume during the drug release test in SBF. Therefore, 30% of the loaded drug was extruded from the cement system at the initial stage, thereafter being released more slowly. Since the heterogeneous system consisting of the cement and the drug-loaded pellet avoided this effect, the drug was released more slowly than from the homogeneous drug-loaded cement. The heterogeneous system using the hardened cement after soaking in SBF at 37 degrees C for 10 days released the drug very slowly at the initial stage since it avoided the drug squeezing effect, and the release continued slowly for more than 300 h.