A Novel Skeletal Drug Delivery System Using Self-Setting Bioactive Glass Bone Cement IV: Cephalexin Release From Cement Containing Polymer-Coated Bulk Powder

A novel device consisting of Eudragit-coated cephalexin as a model drug and a self-setting bioactive cement based upon CaO-SiO₂-P₂O₅ glass was investigated. The glass cement hardened within 5 min of 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 37deg;C continued for over 2 weeks. The hardened cement gradually formed low-crystallinity hydroxyapatite and decreased in volume by about 5% during drug release in SBF. Consequently, 30% of the loaded drug was initially released from the homogeneous cement system, and thereafter it was released more slowly. Since the heterogeneous system consisting of the cement and a 50% polymer coated, drug-loaded pellet avoided this drug's burst, the drug was released over a longer period than that in the homogeneous system. The heterogeneous system released the polymer-coated drug very slowly, because it completely avoided the initial burst, and sustained the release over a long period.