Bisphosphonates

Bisphosphonates are a family of drugs used to prevent and treat osteoporosis. There are four bisphosphonates currently approved for use in Canada: alendronate (Fosamax ®), etidronate (Didrocal ®), risedronate (Actonel ®) and zoledronic acid (Aclasta®. Also available are: Actonel® Plus Calcium and Fosavance® (Fosamax® with vitamin D).

How do they work?

Bisphosphonates bind to the surfaces of the bones and slow down the bone resorping action of the osteoclasts (bone-eroding cells). This allows the osteoblasts (bone-building cells) to work more effectively.

How effective are they?

All four bisphosphonates increase bone density and prevent fractures of the spine (vertebral fractures). Alendronate, risedronate and zolendric acid have also been shown to prevent hip fractures. 

Who can take them?

Bisphosphonates are used to treat osteoporosis in: postmenopausal women and in men; and in men and women of any age who are using steroid medications.

How are they taken?

There are very specific instructions about how bisphosphonates must be taken. Following the directions will allow your body to absorb the drug properly and may help you avoid side effects. Because calcium interferes with the absorption of bisphosphonates, calcium supplements must be taken at other times of the day. See table below.

Are there side effects?

The most common side effects are nausea, abdominal pain and loose bowel movements. Bone, joint and/or muscle pain has been reported in patients taking bisphosphonates; such reports have been infrequent. There is a small risk of ulcers in the esophagus with both alendronate and risedronate, especially if taken incorrectly. The most common side effects of zoledronic acid, which usually only last a day or two, are fever, pain in the muscles, bones or joints, flu-like symptoms and headache. There have been rare cases of acute renal dysfunction following infusions of zoledronic acid. 

 In very rare cases, alendronate, risedronate and zoledronic acid have been linked to a breakdown of the jaw bone (called osteonecrosis of the jaw) following dental surgery such as dental extractions. Rare cases of atypical fractures of the femoral (thigh) bone have been reported with bisphosphonates. Notify your physician if you experience pain in the groin or thigh that is present for a few weeks. Read more>>

How to take a bisphosphonate