Long-term strontium ranelate administration in monkeys preserves characteristics of bone mineral crystals and degree of mineralization of bone

Introduction: Strontium ranelate simultaneously increases bone formation and decreases bone resorption, leading to prevention of bone loss and increase in bone mass and bone strength in normal and ovariectomized rats. This study investigated the interactions of stable strontium (Sr) with bone mineral in monkeys after long-term strontium ranelate treatment and after a period of treatment withdrawal. Materials and Methods: Iliac bone was obtained from untreated monkeys, monkeys at the end of a 52-week strontium ranelate administration (200, 500, 1250 mg/kg/day orally), and in parallel groups 10 weeks after the end of strontium ranelate administration (same three doses; n = 3-7). Sr uptake and distribution in bone mineral were quantified by X-ray microanalysis, changes at the crystal level by X-ray diffraction, and the degree of mineralization of bone (DMB) by quantitative microradiography. Results: After strontium ranelate administration, dose-dependent Sr uptake occurred into cortical and cancellous bone, with higher content (1.6 times) in new than in old bone. This Sr uptake decreased (50%) 10 weeks after treatment withdrawal; the decrease occurred almost exclusively in new bone. At the end of strontium ranelate treatment and after its withdrawal, a preservation of crystal characteristics was observed, suggesting that Sr was only faintly linked to crystals by ionic substitution and of DMB. Conclusions: These results show the absence of a deleterious effect of long-term strontium ranelate treatment on bone mineralization, confirming the histomorphometric observations made in postmenopausal osteoporotic women treated with strontium ranelate.