Bisphosphonates are medications that used to treat bone loss and are the most common agent to be prescribed for osteoporosis. These drugs can also reduce fracture risk in cases of previous fracture. Bone is constantly undergoing a turnover process in which osteoblasts create bone and osteoclasts destroy it. Bisphosphonates inhibit the actions of osteoclasts by promoting their apoptosis (programmed cell death), which, in turn, slows bone loss.
Benefits of bisphosphonates
Bisphosphonates slow ongoing bone damage, reduce bone pain and prevent abnormally high blood levels of calcium. In cancer patients with bone damage, bisphosphonates reduce the need for radiotherapy as well as reducing the risk of fracture. Overall, these drugs improve a patient’s chance of healing and recovering bone strength, which leads to an improved quality of life.
Uses of bisphosphonates
Bisphosphonates are used in bone diseases such as osteoporosis and Paget’s disease. In osteoporosis, bones become brittle and may fracture easily. In Paget’s disease, abnormal bone forms which can cause deformity and pain. The two most commonly prescribed bisphosphonates in the treatment of osteoporosis are alendronate and risedronate.
Classes of bisphosphonates
Bisphosphonates can be divided into two classes, which include:
- The nitrogenous bisphosphonates such as palmidronate, alendronate and zoledronate
- The non-nitrogenous bisphosphonates such as etidronate, clodronate and tiludronate.
The two types of bisphosphonates differ in their mechanism of action for killing osteoclast cells.
Dosage and administration
Bisphosphonates are usually taken as tablets but can also be given by injection. These drugs can cause gastrointestinal irritation and should be taken with water on an empty stomach in the morning. Patients are advised to then wait for at least half an hour before eating or taking any other medications. They should also not lie down for 30 minutes after taking these tablets. For osteoporosis, treatment with bisphosphonates is usually given for at least five years depending on progress. For Paget’s disease, the treatment may be given for a shorter period of time.
The most common side effect of bisphosphonate therapy is gastrointestinal irritation. This may give rise to stomach pain, heartburn, nausea, vomiting, constipation or diarrhoea. Other side effects include dizziness, headache, mouth ulcers and muscle and joint pain. A potentially serious but very rare side effect of bisphosphonate therapy is osteonecrosis of the jaw, which can destroy the jaw bone.
Reviewed by Sally Robertson, BSc