BISPHOSPHONATES
The most common family of drugs used to treat osteoporosis
Bisphosphonates are the most common family of drugs used to treat osteoporosis. They are part of the group of osteoporosis medications known as anti-resorptives. There are four bisphosphonates currently approved for use in Canada: alendronate (Fosamax ®), etidronate (Didrocal ®), risedronate (Actonel ®) and zoledronic acid (Aclasta®). Also available are: Actonel DR™, Fosavance® (Fosamax® with vitamin D) and several generic versions.
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 reduce the risk of fractures of the spine (vertebral fractures). Alendronate, risedronate and zoledronic acid have also been shown to reduce the risk of hip fractures and fractures of other bones.
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.
| Frequency | Time of day | Instructions | |
| Alendronate (Fosamax®), 10 mg (treatment) |
every day | first thing in morning, at least 1/2 hour before eating | Take with 250ml (8 oz) plain water. Stay upright (don’t bend or lie down) for the first 1/2 hour AND until after the first food of the day |
| Alendronate (Fosamax®) 70 mg (Fosavance®) 70 mg + 2800 IU vitamin D or 70 mg + 5600 IU vitamin D |
once a week | same as above | same as above |
| Etidronate (Didrocal®) 400 mg |
The white etidronate tablet is taken daily for two weeks followed by a blue calcium tablet taken daily for an additional 10 weeks | Take the white etidronate tablet (first two weeks) mid morning, mid afternoon or evening (at least two hours before and after eating)Take the blue calcium tablet (next 10 weeks) with food | Take the white etidronate tablet with a full glass of water. Do not eat or take any additional supplements or vitamins for 2 hours before or after taking etidronate.Take the blue calcium tablet with food. |
| Risedronate (Actonel®) 5 mg |
every day | first thing in morning, at least 1/2 hour before eating | Take with a full glass of water. Stay upright (don’t bend or lie down) for the first 1/2 hour AND until after the first food of the day |
| Risedronate (Actonel®) 35 mg |
once a week | same as above | same as above |
| (ActonelDR™) 35 mg (DR=delayed release) | once a week | Take first thing in morning WITH breakfast | Take with full glass of water. Stay upright (don’t bend or lie down) for the first 1/2 hour |
| Risedronate (Actonel®) 150 mg |
once a month | first thing in morning, at least 1/2 hour before eating | Take with a full glass of water. Stay upright (don’t bend or lie down) for the first 1/2 hour AND until after the first food of the day |
| Zoledronic acid (Aclasta®) 5 mg |
once a year | not applicable | Given as a 15-minute intravenous (IV) infusion by a certified healthcare professional |
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, and headache. There have been rare cases of kidney dysfunction following infusions of zoledronic acid. In the vast majority of cases, this has been reversible.
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.