Disposition of alendronate following local delivery in a rat jaw

Background: Recently, we have shown that local delivery of alendronate redu ced significantly bone resorption activated by surgical separation of perio steum from bone. These results advocate the use of local application of ale ndronate in bone surgeries to prevent regional bone resorption at the surge ry site. Here we investigated the efficacy of absorbtion of alendronate by the bone from a gelatin sponge soaked with radiolabeled alendronate applied topically at the surgical site. Methods: Following elevation of the mucoperiosteal flap next to premolars a nd molars of the rat mandible, a gelatin sponge soaked with 10 mu l of radi olabled alendronate (1 mu Ci/mg) was applied to exposed bone on one side. T he local absorbtion of alendronate and its disposition in the contralateral side of the mandible as well as in the tibia bone were analyzed. Results: The results show that 10% of total alendronate content of the gela tin sponge was absorbed in the bone locally (in the surgical site), while 0 .2% was disposed in the tibia. Of interest is the fact that the surgical wo und in the contralateral side increased the disposition of alendronate up t o 2%. This finding is most likely the result of extravasation and diffusion of alendronate due to surgical wounding. Conclusion: This study strongly supports our notion that local delivery of alendronate and its affinity to bone may become a very important treatment modality to prevent resorption of bone during dental and orthopedic procedu res.