Bisphosphonates are a group of drugs that can be used to help protect bones against the effects of some cancers and to treat some bone conditions. Sometimes bisphosphonates are called bone strengthening or bone hardening treatments.
Bisphosphonates may be used to treat multiple myeloma and bone metastases.
How bisphosphonates work
Bisphosphonates slow down the action of bone cells (osteoclasts) that dissolve small bits of bones to help remodel them and keep them strong. When cancer spreads to the bone (metastasizes), these cells become overactive, causing the bone to be destroyed faster than it’s rebuilt. When this happens, the damage can cause bones to become thinner and weaker causing:
- pain in the affected bones
- high calcium levels in the blood (hypercalcemia)
- an increased risk of bones breaking (fracturing)
Uses of bisphosphonates
Bisphosphonates slow down the breakdown of bones. They may be used to:
- reduce bone pain caused by bone metastases or multiple myeloma
- reduce high levels of calcium in the blood
- help strengthen bone and reduce the risk of breaks caused by cancer, bone metastases or osteoporosis
Most cancers that affect the bones have started in another part of the body and have spread to the bone. The most common types are breast cancer, prostate cancer and lung cancer. Cancer pain is often linked to bone metastases.
Multiple myeloma is a cancer of abnormal plasma cells (a type of white blood cell) that collect in the bone marrow. These abnormal cells make a substance that leads to bone damage and bone pain.
When bone metastases and multiple myeloma cause bones to break down, calcium moves out of the bones and into the bloodstream. This can cause calcium levels in the blood to rise. A high level of calcium in the blood is called hypercalcemia. This can also cause bones to become weak and fragile so that they break easily.
A loss of bone mass (or bone density) is called osteoporosis. This condition causes bone to become weak and more likely to break. Some cancer treatments, such as long-term corticosteroid use, hormonal therapies and some chemotherapy drugs can increase the risk of osteoporosis. Osteoporosis can also happen because of factors not related to cancer. Bisphosphonates may be used to prevent and treat osteoporosis.
Types of bisphosphonates
The type of bisphosphonate used can depend on the type of cancer being treated. Common bisphosphonates used to treat bone metastases and multiple myeloma include:
- clodronate (Bonefos) given by mouth or by an intravenous (IV) infusion (through a vein)
- pamidronate (Aredia) given by an IV infusion
- zoledronic acid (Zometa) given by an IV infusion
Bisphosphonates used to prevent and treat osteoporosis include alendronate (Fosamax), risedronate (Actonel) and etidronate (Didrocal, Didronel).
Bisphosphonates can be taken as pills or by an IV infusion.
Pills are usually taken once or twice per day on an empty stomach.
IV infusions are usually given every 3 to 4 weeks. They can take anywhere from 15 minutes to 4 hours, depending on which bisphosphonate is given. They can be given at the hospital or at home by a homecare nurse.
Follow-up after bisphosphonates
Follow-up when bisphosphonates are given includes:
- checking to see if bone pain has lessened
- blood chemistry tests to check how the kidney is working and calcium level
- a bone density scan
Side effects can happen with any type of treatment, but everyone’s experience is different. Some people have many side effects. Other people have few or none at all.
If you develop side effects, they can happen any time during, immediately after or a few days or weeks after bisphosphonate therapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.
Side effects of bisphosphonate therapy will depend mainly on the type of bisphosphonate, the dose, how the drug is given and your overall health. Tell your healthcare team if you have these side effects or others you think might be from bisphosphonates. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.
The following are some side effects of bisphosphonate therapy.
Fatigue is a general lack of energy and tiredness that can happen during bisphosphonate therapy. Fatigue makes a person feel more tired than usual and can interfere with daily activities and sleep. It tends to be worse when you are also having other treatments, such as chemotherapy or radiation therapy.
Increased bone pain
Sometimes bone pain can temporarily become worse when you first take bisphosphonates. This side effect is often temporary. You may be given stronger pain relievers until this side effect goes away.
Digestive problems can happen, especially when the bisphosphonate is taken as pills. Digestive problems include:
Flu-like symptoms can happen shortly after bisphosphonates are given. They include fever, chills, muscle and joint aches or pain and headaches. These side effects do not usually happen and are often temporary. They are more likely to happen after bisphosphonates are given by an IV infusion.
Low calcium levels
Bisphosphonates can lower blood calcium to below normal levels. This side effect does not usually happen and is often temporary. Calcium levels in the blood are often checked when you are given bisphosphonates.
Change in how the kidney works
Bisphosphonates can affect how the kidney works. It does not often cause any symptoms. Blood tests to check the kidney are done while you are taking bisphosphonates.
Osteonecrosis is the death of bone caused by poor blood supply to the area. Osteonecrosis of the jaw bone underneath the teeth is a rare side effect of some bisphosphonates if they are taken for over a year. It is sometimes seen when a tooth is pulled in someone who is taking bisphosphonates. Osteonecrosis is not usually seen in people who take bisphosphonates as pills.
Osteonecrosis can cause loosening of the teeth and tooth loss and infection or open sores of the jaw bone that don’t heal. These sores are often hard to treat.
You may be advised by your doctor to get a dental check-up and have tooth or jaw problems treated before starting to take bisphosphonates. Maintaining good oral hygiene, making sure your dentures are well fitted and having regular dental check-ups might help prevent osteonecrosis of the jaw.
Information about specific cancer drugs
Details on specific drugs change regularly. Find out more about sources of drug information and where to get details on specific drugs.
Any steroid hormone that acts as an anti-inflammatory by reducing swelling and lowering the body’s immune response (the immune system’s reaction to the presence of foreign substances).
Corticosteroids are made by the adrenal gland. They can also be produced in the lab.
Treatment that adds, blocks or removes hormones.
Hormonal therapy is used to slow or stop the growth of cancer cells that depend on hormones to grow. Hormonal therapies include using drugs, surgery or radiation therapy to change hormone levels.
Also called hormone therapy, hormone treatment and endocrine therapy.
I’m extremely grateful to the Canadian Cancer Society for funding my research with an Innovation Grant.
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