Changes in the drug release pattern of fresh and set simvastatin-loaded brushite cement

Calcium phosphate cements are synthetic bone graft substitutes able to set at physiological conditions.They can be applied by minimally invasive surgery and can also be used as drug delivery systems.Consequently, the drug release pattern from the cement paste (fresh cement) is of high clinical interest.However, previous studies have commonly evaluated the drug release using pre-set cements only.Therefore, the aim of this work was to determine if the time elapsed from cement preparation untilimmersion in the solution (3 min for fresh cements, and 1 h and 15 h for pre-set cements) had aninfluence on its physical properties, and correlating these to the drug release profile. Simvastatin wasselected as a model drug, while brushite cement was used as drug carrier. This study quantified howthe setting of a material reduces the accessibility of the release media to the material, thus preventingdrug release. A shift in the drug release pattern was observed, from a burst-release for fresh cements toa sustained release for pre-set cements