ATC Group: M05BA Bisphosphonates

Alendronic acid is a bisphosphonate that inhibits osteoclastic bone resorption with no direct effect on bone formation. The bone formed during treatment with alendronic acid is of normal quality.

Clodronic acid is a bisphosphonate, (formerly diphosphonates), a group of analogues of pyrophosphate, which have been shown, in vitro, to inhibit the formation and dissolution of calcium phosphate (hydroxyapatite). In vivo, they have been shown to inhibit bone resorption to a greater or lesser extent, depending on the compound, and clodronate is one of the most effective in this respect.

Etidronate acts primarily on bone. It can inhibit the formation, growth, and dissolution of hydroxyapatite crystals and their amorphous precursors by chemisorption to calcium phosphate surfaces.

Ibandronic acid belongs to the bisphosphonate group of compounds which act specifically on bone. Their selective action on bone tissue is based on the high affinity of bisphosphonates for bone mineral. Bisphosphonates act by inhibiting osteoclast activity, although the precise mechanism is still not clear. In vivo, ibandronic acid prevents experimentally-induced bone destruction caused by cessation of gonadal function, retinoids, tumours or tumour extracts.

The principal pharmacologic action of pamidronic acid is inhibition of bone resorption. Although the mechanism of antiresorptive action is not completely understood, several factors are thought to contribute to this action. Pamidronic acid adsorbs to calcium phosphate (hydroxyapatite) crystals in bone and may directly block dissolution of this mineral component of bone.

Risedronic acid is a pyridinyl bisphosphonate that binds to bone hydroxyapatite and inhibits osteoclast-mediated bone resorption. The bone turnover is reduced while the osteoblast activity and bone mineralisation is preserved.

Tiludronic acid is indicated for treatment of Paget’s disease of bone (osteitis deformans). In vitro studies indicate that tiludronate disodium acts primarily on bone through a mechanism that involves inhibition of osteoclastic activity with a probable reduction in the enzymatic and transport processes that lead to resorption of the mineralized matrix.

Zoledronic acid belongs to the class of bisphosphonates and acts primarily on bone. It is an inhibitor of osteoclastic bone resorption.