Bisphosphonates are a class of drug prescribed to prevent bone loss in people.
Bones undergo constant turnover with osteoblast forming bone and osteoclasts resorbing it. In normal bone tissue, there is a balance between bone formation and bone resorption. But in diseased bone tissue, this balance is disrupted.
Clodronate, the active ingredient in OSPHOS, is a bisphosphonate that in laboratory animal studies and in vitro studies is known to inhibit bone resorption by reducing number of active osteoclasts, regardless of the cause of osteoclast activity and it inhibits the formation and dissolution of calcium phosphate crystals in the bone matrix. Ultimately these actions lead to a decrease in the breakdown of bone.
While the exact mechanism of action of bisphosphonates in the horse is unknown this is the understood clinical pharmacology regarding clodronate at a cellular level and in other species.