Calcitonin release system in the treatment of experimental osteoporosis. Histomorphometric evaluation.

Bioabsorbable polyphosphazene matrices charged with 250 microg calcitonin were evaluated as calcitonin delivery systems for the controlled release of this drug in an in vivo experimental model. Matrices were implanted under general anesthesia in osteopenic female rats, while a group of osteopenic animals (control group) received unloaded matrices. After 30 days a second series of matrices, loaded and unloaded was, respectively, implanted in both groups. In a third group of osteopenic female rats (positive control), 10 IU calcitonin were injected daily for two months. A baseline group and a sham operated group of animals were also included in the study. The explanted matrices were histologically evaluated together with the surrounding tissues, and bone histomorphometry was performed on undecalcified sections from femurs. The results showed the good biocompatibility of the matrices. Bone histomorphometry revealed that bone architecture in the treatment group was improved and results were not different from those observed after calcitonin injection. These data confirm a good in vivo behavior of the system, as well as a therapeutic effect of the released calcitonin in the osteopenic condition.