Local drug delivery system using ceramics: vacuum method for impregnating a chemotherapeutic agent into a porous hydroxyapatite block

We performed an experimental study on a new drug delivery system that emplo ys a porous hydroxyapatite block (HAb) (com position: Ca-10(PO4)(6)(OH)(2)) to conduct sustained release of a chemotherapeutic agent. To confirm penet ration of the agent into the HAb (2 cm(3)), an aqueous solution containing eosin dye was used at various vacuum pressures. To estimate the storage cap acity of the HAb, blocks were weighed before and after being impregnated wi th the aqueous dye solutions, and the capacity of the block was calculated from the increase in weight after vacuum. In this slow-release study using vacuum, the anti-cancer drug methotrexate (MTX) was used in vitro. Four HAb (1 cm(3)) containing different concentrations of MTX, ranging from 1.22 to 2.38 mg per block, were studied. All were found to release the drug, maint aining a mean concentration of 0.22 to 0.32 mu g/ml even after twelve days. This concentration is high enough to be effective against tumor cells. The results suggest that HAb impregnated with a chemotherapeutic agent using a simple vacuum system may serve as a valuable new method of administering l ocal chemotherapy, primarily when used as a strut graft for bone defects. T his new drug delivery system can also be used as an adjuvant material in ex tended curettage, which can also discourage recurrence of benign tumors wit hout any risk of systemic toxicity. (C) 1999 Kluwer Academic Publishers.