ABSTRACT
A number of calcium phosphate materials have been investigated as drug release matrices for the prophylactic treatment of implant-related osteomyelitis. However, some studies have shown the influence of processing on the efficacy of the delivered drug. The objective of this study was to evaluate the influence of pH during processing on the efficacy of vancomycin hydrochloride (VH) against Staphylococcus aureus. VH was loaded into a brushite cement (CaHPO(4).2H(2)O; pH 2.4); a hydroxyapatite cement (Ca(10)(PO(4))(6)OH(2); pH 9.4); and an apatite xerogel (pH 7.4). The pH of the material during processing had a significant influence on the mechanism of release from the cement. VH released from the apatite cement (pH 9.4) was not released in accordance with the Higuchi model. In addition to affecting release, the basic pH was shown to diminish the antibacterial potency of the released VH. Despite exceeding the minimum inhibitory concentration, the eluent from the apatite cement was ineffective against a culture of S. aureus. The findings of this study reinforce the importance of evaluating not only the release of the drug from the material matrix but also the antibacterial potency of the released drug.
