Alendronate sodium is a bisphosphonate that acts as a specific inhibitor of osteoclastmediated bone resoprtion.  Bishosphonates are synthetic analogs of pyrophosphate that bind to the hydroxyapatite found in bone. 

Alendronate is indicated for the treatment of osteoporosis in postmenopausal women. In postmenopausal women, alendronate increases bone mass and reduces the incidence of fractures, including those of the hip and spine.  It is also indicated for the prevention of postmenopausal osteoporosis.