Strontium ranelate--data on vertebral and nonvertebral fracture efficacy and safety: mechanism of action.

Strontium ranelate is a novel therapy for the treatment of postmenopausal osteoporosis with actions to reduce bone resorption and increase bone formation. In vitro, strontium ranelate has anabolic and antiresorptive activity, increasing collagen and non-collagen protein synthesis, enhancing pre-osteoblast differentiation, inhibiting osteoclast differentiation, and reducing osteoclast function. In animal models, the increase in bone density is closely correlated with increases in biomechanical bone strength. Histomorphometry demonstrates reduced osteoclast surfaces with increased bone formation. Clinical trials in postmenopausal women have demonstrated 3-year fracture efficacy. Reductions in vertebral fracture were seen in patients with and without prevalent vertebral fracture. Nonvertebral fractures were also significantly reduced. In a subgroup of patients at high risk for hip fracture, there was a significant reduction in hip fracture risk. Strontium ranelate is well tolerated with nausea, diarrhea, headache, and dermatitis more frequent in treated patients only for the first 3 months of therapy. Together, these data suggest that strontium ranelate is a well-tolerated and effective therapy for postmenopausal osteoporosis reducing vertebral and nonvertebral fracture by a novel dual antiresorptive and anabolic action on bone.