Bone tissue undergoes constant remodeling and is kept in balance (homeostasis) by osteoblasts creating bone and osteoclasts destroying bone. Bisphosphonates inhibit the digestion of bone by encouraging osteoclasts to undergo apoptosis, or cell death, thereby slowing bone loss.
The uses of bisphosphonates include the prevention and treatment of osteoporosis, Paget's disease of bone, bone metastasis (with or without hypercalcaemia), multiple myeloma, primary hyperparathyroidism, osteogenesis imperfecta, fibrous dysplasia, and other conditions that exhibit bone fragility.
Bisphosphonates are used to treat osteoporosis, osteitis deformans (Paget's disease of the bone), bone metastasis (with or without hypercalcaemia), multiple myeloma, and other conditions involving fragile, breakable bone.
In osteoporosis and Paget's, the most popular first-line bisphosphonate drugs are alendronate and risedronate. If these are ineffective or if the person develops digestive tract problems, intravenous pamidronate may be used. Strontium ranelate or teriparatide are used for refractory disease. The use of strontium ranelate is restricted because of increased risk of venous thromboembolism, pulmonary embolism and serious cardiovascular disorders, including myocardial infarction. In postmenopausal women, the selective estrogen receptor modulator raloxifene is occasionally administered instead of bisphosphonates. Bisphosphonates are beneficial in reducing the risk of vertebral fracture in steroid induced osteoporosis.
Long-term treatment with bisphosponates produces anti-fracture and bone mineral density effects that persist for 3–5 years after an initial 3–5 years of treatment. The bisphosphonate alendronate reduces the risk of hip, vertebral, and wrist fractures by 35-39%; zoledronate reduces the risk of hip fractures by 38% and of vertebral fractures by 62%. Risedronate has also been shown to reduce the risk of hip fractures.