Bisphosphonates and nephrocalcinosis in a rabbit leg lengthening model: a histological and therapeutic comparison

We performed a comparison of the effects of two bisphosphonates, pamidronate and zoledronic acid, on regenerate bone mineral content in distraction osteogenesis in an immature rabbit model. Single dose zoledronic acid was found to be 18 times more potent at producing an increase in bone mineral content than pamidronate per mg/kg of drug infused at surgery. Histological examination of all rabbit kidneys was performed at trial completion. Nephrocalcinosis was identified in 14 of 20 kidneys of rabbits infused with pamidronate, but was not detected in the 20 kidneys of those rabbits infused with zoledronic acid. A further 20 kidneys from rabbits given a second dose of zoledronic acid were also found to be free of signs of nephrocalcinosis. Three of 40 control kidneys exhibited signs of nephrocalcinosis. The increased potency of zoledronic acid allowed us to give one-tenth the dose of pamidronate, with increased therapeutic efficacy and no evidence of nephrocalcinosis.