Bisphosphonates

Bisphosphonates (BPs) are the medications most commonly prescribed to treat osteoporosis. They prevent bone loss and reduce the risk of fractures.

How They Work

These drugs are similar to a natural bone material called pyrophosphate. BPs are similar enough to bind strongly to existing bone and become embedded in the skeleton. They prevent further bone loss and create a "protective layer" that slows down osteoclast activity from dissolving tissue on the bone's surface.

Bisphosphonates Available in Canada

The bisphosphonates available in Canada include:

• Etidronate (available as Didronel® or, when supplemented with calcium carbonate, Didrocal®) – approved for the prevention and treatment of post-menopausal osteoporosis. Etidronate is taken on a cyclical basis, ie. for two weeks out of every 3-month period.
• Alendronate (Fosamax®) – approved for the prevention and treatment of post-menopausal osteoporosis.
• Risedronate (available as Actonel®) – approved for the prevention and treatment of post-menopausal osteoporosis. Risedronate is also available with calcium.
• Zoledronic acid (Aclasta®, known as Reclast® in the US) – approved by Health Canada in 2007 for the treatment of osteoporosis in post-menopausal women. This prescription medication is purchased by the patient and then administered by a health professional intravenously, for 15 minutes once a year.

How Effective Are Bisphosphonates?

All four BPs have the potential to slow down bone loss and increase bone density. These medications have the potential to reduce the risk of fractures for both men and women who have osteoporosis.

Alendronate (Fosamax), risedronate (Actonel) and zolendric acid have all been shown to significantly reduce a woman’s risk of fracture in the spine, hip and other bones. Etidronate is the least effective of the four drugs.

Place in Osteoporosis Therapy

With the emerging data about the effectiveness of the newer BPs, alendronate and risedronate are now considered "first-line" agents for the treatment of post-menopausal osteoporosis.

Use this link for more information about how to take BPs, their side effects and costs.

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