[Long-term and high-dose bisphosphonate administration causes no bone over-mineralization].

Objective: To evaluate the effects of long-term bisphosphonate administration (incadronate) upon the mean degree of secondary bone mineralization.

Methods: Thirty adult beagles were divided randomly into three groups of CNT, YML and YMH based upon their body weights (5 males and 5 females in each group). Animals in CNT were orally given lactose 12 mg x kg(-1) x d(-1) while those in YML and YMH were orally given incadronate disodium at doses of 0.3 mg x kg(-1) x d(-1) and 0.6 mg x kg(-1) x d(-1) respectively. The dosing procedure lasted for three years. Prior to sacrifices, all animals were double-labeled intravenously with oxytetracycline hydrochloride (20 mg x kg(-1)). After necropsy, the left 9th ribs were excised for evaluation.

Results: Histomorphometry showed that activation frequency in YML and YMH [(4.93 +/- 0.92)/mm(2) and (2.50 +/- 0.78)/mm(2)] were significantly lower than that in CNT (7.83 +/- 0.96)/mm(2) per year. The mean degree of mineralization in bone in YML and YMH (1.40 +/- 0.12, 1.48 +/- 0.09) were significantly higher than CNT (1.07 +/- 0.06). The increments were 31% and 38% respectively.

Conclusion: Long-term and high-dose bisphosphonate administration significantly suppresses bone turnover so as to increase the degree of bone mineralization. But there is no resulting bone over-mineralization. (incadronate) administration on the mean degree of secondary mineralization in bone.