BISPHOSPHONATES
The most common family of drugs used to treat osteoporosis
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 three bisphosphonates currently approved for use in Canada: alendronate (Fosamax ®), risedronate (Actonel ®) and zoledronic acid (Aclasta®). Also available are Actonel DR™(DR= delayed release), Fosavance® (alendronate with vitamin D).
How Do They Work?
Bisphosphonates bind to the surfaces of the bones and slow down the bone resorpting action of the osteoclasts (bone-eroding cells). This allows the osteoblasts (bone-building cells) to work more effectively.
How Effective Are They?
All bisphosphonates reduce the risk of fractures.
Who Can Take Them?
Bisphosphonates are used to treat osteoporosis in children, men and women at high risk of fracture.
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®) 70 mg (Fosavance®) 70 mg + 2800 IU vitamin D or 70 mg + 5600 IU vitamin D | once a week | 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®), 10 mg (treatment) |
everyday | first thing in morning, at least 1/2 hour before eating | Take with 250 ml (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. |
| 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 | 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 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 common possible side effects are nausea, abdominal pain and loose bowel movements. Flu like symptoms can be experienced with both oral or IV zoledronic acid (more common with IV than oral). Bone, joint and/or muscle pain has been reported in patients taking bisphosphonates; such reports have been infrequent. 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 or low calcium 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 jawbone (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.