Bisphosphonates - What are Bisphosphonates?

In pharmacology, bisphosphonates (also called diphosphonates) are a class of drugs that prevent the loss of bone mass, used to treat osteoporosis and similar diseases.

Bone has constant turnover, and is kept in balance (homeostasis) by osteoblasts creating bone and osteoclasts digesting bone. Bisphosphonates inhibit the digestion of bone by osteoclasts.

Osteoclasts also have constant turnover and normally destroy themselves by apoptosis, a form of cell suicide. Bisphosphonates encourage osteoclasts to undergo apoptosis.

The uses of bisphosphonates include the prevention and treatment of osteoporosis, osteitis deformans ("Paget's disease of bone"), bone metastasis (with or without hypercalcaemia), multiple myeloma, primary hyperparathyroidism, osteogenesis imperfecta and other conditions that feature bone fragility.

Bisphosphonates were developed in the 19th century but were first investigated in the 1960s for use in disorders of bone metabolism.

Their non-medical use was to soften water in irrigation systems used in orange groves. The initial rationale for their use in humans was their potential in preventing the dissolution of hydroxylapatite, the principal bone mineral, thus arresting bone loss.

Only in the 1990s was their actual mechanism of action demonstrated with the initial launch of Fosamax (alendronate) by Merck.

All bisphosphonate drugs share a common P-C-P "backbone":

The two PO₃ (phosphonate) groups covalently linked to carbon determine both the name "bis''phospho''nate" and the function of the drugs.

The long ''side-chain'' determines the chemical properties, the mode of action and the strength of bisphosphonate drugs. The short ''side-chain', often called the 'hook', mainly influences chemical properties and pharmacokinetics.

Further Reading

• Bisphosphonate Mechanism
• Bisphosphonate Uses
• Bisphosphonate Side-Effects

This article is licensed under the Creative Commons Attribution-ShareAlike License. It uses material from the Wikipedia article on "Bisphosphonate" All material adapted used from Wikipedia is available under the terms of the Creative Commons Attribution-ShareAlike License. Wikipedia® itself is a registered trademark of the Wikimedia Foundation, Inc.