What are the bisphosphonates?

When women reach around 50 years old, as the estrogen level in their bodies decreases, they gradually enter menopause. In addition to experiencing menopausal symptoms, menopausal women have another very serious problem that is generally not taken seriously, which is calcium loss. Menopausal women are prone to osteoporosis. The function of bisphosphonates is to restore and function bone cells to normal levels, reduce bone loss, and thus reduce the occurrence of osteoporosis.

Bisphosphonates, like estrogen, can cause a false appearance of bone growth because bone-specific growth processes are not stopped until they are complete. We used the analogy of building a house, in which the growth process of the bone is like a room that is partially rebuilt. The construction work continues until it is completed, and the house looks brand new after it is built. However, the number of houses did not actually increase; it was just that a construction project that had already started was completed. This process can increase bone size by 5% to 10% (you'll see this figure in most reports). But the growth process only lasts for a few years, after which osteoporotic activity decreases and then stops altogether—both growth and resorption processes cease.

This is why we are cautious about long-term use of bisphosphonates. Bones remodel throughout your life. If you gain mass in your spinal cord, the bones in your pelvis and legs increase in density to carry the extra weight. If you have arthritis and start walking differently (like leaning to one side) to avoid hip pain, the bone density in the weight-bearing hip and leg will increase. What if the bones are broken? You need to repair the bones. So you can't block all bone renewal.

With this in mind, doctors use first-generation bisphosphonates such as didronel as an intermittent oral medication for 3 months, followed by 3 months off. Osteomalacia has been reported in women who took Etidronate for four years. Newer bisphosphonates (eg, alendronate) are less tightly bound to bone, so it is thought (but not proven) that continuous administration of these bisphosphonates is possible.

A New Zealand study tested bone renewal in women who took first-generation bisphosphonates for 5 to 9 years and then stopped the medication. The researchers found that the inhibition of bone turnover was reversible once the drug was stopped, but the benefits of increased bone density and reduced fractures lasted for at least 2 years. Until now, we did not know how long the correct course of treatment should be, but this study suggests that it is not necessary to know the exact duration of treatment.

Bisphosphonates do help. The Fracture Intervention Trial (FIT) first studied people with low bone density and previous vertebral fractures. Alendronate (Copan) reduces hip and wrist fractures by 50% and all clinical (symptomatic) fractures by 28%. But only 10% to 15% of postmenopausal women have a vertebral fracture, so they added a second study to investigate postmenopausal women with low bone density but no vertebral fractures after four years of treatment. Women diagnosed with osteoporosis by bone mineral density (T-score less than -2.5) had a reduced risk of all clinical fractures, hip fractures, and vertebral deformities after 4 years of alendronate treatment, but there was no such change in women with osteopenia (T-score less than -2.5). This result emphasizes that bone density is only one of the risk factors for fractures; bone fragility is also important. It has been shown that women who have had fractures have very brittle bones. Women with very low bone density are also at risk for osteoporosis, but women with slightly lower bone density are not at as great a risk as women with brittle bones. With these data, most experts no longer recommend that women with osteopenia take bisphosphonates. This is done not only because alendronate has little benefit but also because most of the anti-fracture effect of alendronate is due to its ability to prevent bone loss, which occurs early and does not increase over time.