Bones are like a bank; your bone "balance" stays healthy as long as you're not taking out more than you put in. That analogy may be a little simplistic but in essence, bone strength depends upon the balance between the bone cells that build bone versus those cells that break down bone.
Researchers have used the "bone strength equals bone buildup minus bone loss" formula to develop drugs that prevent and treat bone loss. Drugs that slow down bone breakdown are referred to as antiresorptive drugs. The wonderful part of antiresorptive drugs is that not only do they build bone density, but they also actually reduce the frequency of bone fracture.
Bisphosphonates are a type of antiresorptive drug that inhibits bone removal by the osteoclasts. Taking bisphosphonates can increase bone density in both the hip (by 3 percent) and lumbar spine (by 5 percent). Changes in bone density can be seen in the first year of treatment. Fracture rates are reduced by 50 percent.
Using alendronate, ibandronate, and risedronate
The most commonly used antiresorptive drugs belong to a class of compounds referred to as bisphosphonates, also called diphosphonates. Three oral bisphosphonates are approved in the United States for both prevention and treatment of osteoporosis:
- Alendronate (Fosamax)
- Ibandronate (Boniva) (the newest drug, it may be difficult to find)
- Risedronate (Actonel)
All bisphosphonates bind to osteoclasts (cells that break down bone) and slow their ability to resorb bone. The drugs differ somewhat in their chemical makeup, but all are antiresorptive drugs, with alendronate being the first developed.
You may find that you tolerate one drug better than the other. For example, alendronate may cause you more difficulty with stomach irritation, and risedronate may not. Ibandronate may be your choice because it only needs to be taken once a month. All the bisphosphonates vary in their side effects and their dosing regimens. People also respond to different drugs differently, so if you start with one and have side effects, don't hesitate to tell your doctor!
You may hear alendronate, ibandronate, and risedronate called "diphosphonates" instead of "bisphosphonates." A diphosphonate is the same thing as a bisphosphonate; just chalk it up to the idiosyncrasies of the scientific world to have two words (long ones, at that) for the same thing. The prefix bis- and di- both refer to the word "two." These drugs contain two phosphonate groups attached to one carbon atom. This particular structure is responsible for the strong binding of the drug to osteoclasts.
Deciding when to treat with bisphosphonates
When is it time to start bisphosphonates? When everyone else in your bridge group is on them? When your children keep hounding you about taking something for your bones? No.
Your doctor makes the final determination of when to start medications for osteoporosis, but she usually follows these guidelines for starting treatment:
- T-score is less than 2.5. (A T-score is the number of standard deviations the bone mineral density measurement is above or below the young normal mean bone mineral density. In other words, your T-score is your score compared to that of young adults.
- T-score is less than 2.0 with multiple risk factors, such as corticosteroid use and low body mass index (BMI).
- T-score is less than 1.5 and you're taking drugs that cause rapid bone loss, such as corticosteroids and phenobarbitol.
- Menopausal status is a factor because rapid bone loss can occur in menopause due to a decrease in estrogen.
Who shouldn't take bisphosphonates?
Not everyone is a good candidate for taking bisphosphonates. Your doctor may decide not to give you bisphosphonates if you have any of the following conditions:
- Esophageal strictures
- Kidney disease
- Severe gastroesophageal reflux
- Vitamin D deficiency
Some people develop side effects that are intolerable, such as stomach irritation, or muscle and joint pain. Sometimes switching from one bisphosphonate to another may help. Among the newer bisphosphonatelike drugs, there is no clear advantage of one medication versus another in preventing fractures.
Taking bisphosphonates with adequate amounts of calcium and vitamin D is critical. You need 1,500 mg of calcium daily and 400 to 800 International Units (IU) of vitamin D daily. Check with your doctor to find out the right amount for you.
Remember that over-the-counter medications, including herbs and homeopathic remedies, are still drugs. Inform your doctor of all medications you take so she can monitor them.
Taking bisphosphonates correctly
Some bisphosphonates can be given in either daily or weekly doses as a preventive. For risedronate (Actonel), the dose is 5 mg daily or 35 mg once a week. Doctors often prescribe alendronate (Fosamax) in a higher dose (10 mg daily or 70 mg once a week). The Food and Drug Administration (FDA) approved ibandronate (Boniva) in 2005 to be taken once a month.
All bisphosphonates need to be taken first thing in the morning with eight ounces of water. Don't eat or drink anything else for 30 minutes after taking your medication. You need to remain upright for about 30 minutes — no sneaking back to bed for a quick nap — to help decrease stomach irritation after taking your medication.
These drugs are absorbed slowly from the gastrointestinal tract. They can cause an irritation of the esophagus (a chemical esophagitis). You must use them with caution if you have any problems with your esophagus. Taking them with water is important because water doesn't compete with the drugs' absorption in the stomach; juice or other foods interfere with absorption.
