Setting characteristics and mechanical behaviour of a calcium phosphate bone cement containing tetracycline

Calcium phosphate cements are used for bone defect filling and they may als o be used as delivery systems for active agents. The physicochemical behavi our of an ionic cement, with a final composition of hydroxyapatite, contain ing tetracycline hydrochloride was investigated. Chemical characterisation, X-ray diffraction analysis, compressive strength and tensile strength were performed. It is known that the antibiotic can be adsorbed on calcium phos phate compounds and the presence of chloride ions can strongly influence th e behaviour of the cement. Adding more than 1% (w/w) of 95% pure tetracycli ne hydrochloride in the solid phase led to a cement with poor mechanical pr operties, but which, in addition to hydroxyapatite, contained residual star ting reagents. For this reason, experiments were also performed with tetrac ycline previously treated with a calcium sulphate solution. Using a treated tetracycline, it was possible to introduce at least 7% (w/w) of active ing redient whilst still allowing the reaction to proceed to completion i.e. th e formation of hydroxyapatite with good mechanical properties. Therefore, t reating the tetracycline HCl with calcium sulphate solution prior to reacti on conserved the activity of the antibiotic, limited the influence of the a ntibiotic on the cement evolution and retained the physical properties of t he cement. (C) 2001 Elsevier Science Ltd. All rights reserved.