Bisphosphonates acts at the cellular level. They act directly or indirectly on the osteoclasts. The effect can be on the formation of osteoclasts and/or on their activity. A decrease in osteoclast number can occur either through direct action on osteoclast precursors, or indirectly by stimulating the osteoblasts to produce an inhibitor of osteoclast formation. Osteoclast inactivation is associated with bisphosphonate uptake from the bone surface.