A NOVEL SKELETAL DRUG-DELIVERY SYSTEM USING SELF-SETTING BIOACTIVE GLASS BONE-CEMENT .2. DRUG-RELEASE FROM A NOVEL SELF-SETTING BIOACTIVE GLASS BONE-CEMENT CONTAINING CEPHALEXIN AND ITS PHYSICOCHEMICAL PROPERTIES

A novel device containing cephalexin as a model drug using a self-sett ing bioactive cement based on CaO-SiO2-P2O5 glass was investigated. Th e device consisted of 95 wt/wt% glass powders and 5 wt/wt% cephalexin powder hardened within 5 min after mixing with a phosphate buffer. Aft er setting, in vitro drug release from homogeneous or heterogeneous dr ug-loaded cement pellets in a simulated body fluid (SBF) at pH 7.25 an d 37 degrees C continued for over 4 weeks. The hardened cement gradual ly formed low-crystallinity hydroxyapatite with high bioactivity in ha rd bone tissue and reduced in volume by about 5% during dissolution te sting in SBF. Consequently, 30% of the loaded drug was squeezed from t he cement system at the initial stage of the drug release, and the rem ainder released more slowly. Because the heterogeneous system consisti ng of the cement and drug-loaded pellet avoided the drug-squeezing eff ect, it showed a longer drug release term than the homogeneous drug-lo aded cement. The heterogeneous system using the hardened cement after soaking in SBF at 37 degrees C for 10 days showed very slow drug relea se at the initial stage because it completely avoided the drug-squeezi ng effect, and the release was a zero-order pattern. (C) 1995 John Wil ey and Sons, Inc.