A new Danish study in the journal, Calcified Tissue International, finds that a lower dose of osteoporosis drugs, also known as bisphosphonates, may actually represent a greater risk by about 50 percent of acute myocardial infarction, or clogging of the coronary vessels, when compared to a higher dose.

Researchers from Aarhus University in Denmark found alendronate (Fosamax), in low doses (10mg), was the problem. Two other drugs, etidronate (Didronel), and raloxifene (Evista) were not associated with an increased risk of acute myocardial infarction (MI), commonly known as a heart attack. That occurs when the blood supply is interrupted due to blockage, causing heart cells to die.

Those patients taking a higher dose (70mg) were found to have a decreased risk for acute MI.

Alendronate was also at a higher risk for atherosclerosis of the coronary artery and vessels, however when taken in higher doses, there was also a protective effect seen.

The results are not conclusive because of the health of the control group.

The data came from a national retrospective cohort in Denmark involving more than 103,000 patients who use bisphosphonates to treat the bone-thinning condition, osteoporosis. They were compared with more than 310,000 individuals matched by age and gender who did not take that class of drugs.

These findings are similar to what was uncovered by Taiwanese researchers. They found that low doses of alendronate were associated with a higher risk of cardiovascular disease than a higher dose.

There may be some association between use of bisphosphonates to treat osteoporosis and increased calcium deposits in the blood vessels, not in the bones where the calcium is needed to increase the strength of the bone.

The jury is still out on these drugs. 

The FDA says it is conducting an ongoing review of the risk of esophageal cancer from taking oral osteoporosis drugs. One study found a doubling of the risk of esophageal cancer among those who had taken the drugs for more than three years or who had 10 or more prescriptions. Necrosis of the jaw has been associated with bisphosphonates as well as a deterioration of the femur, which is the strongest bone in the body. An atypical femur fracture was found in one study to have occurred among several members of the study group, 82% of which had been taking bisphosphonates.

Bisphosphonates were introduced in the mid-1990s to address bone-thinning, which affects mainly women but also can affect men. The drugs work by interfering with the natural cycle of bone loss and rebuilding. As we age, the rebuilding phase seems to decline. Bisphosphonates interfere with the bone loss phase. It may be this slowing of the bone loss phase that leaves older brittle bones behind longer which may contribute to the unusual fracture risk.

Weight bearing exercise is known to help, as do supplements vitamins D, K2, and calcium paired with magnesium.

The FDA meanwhile still believes bisphosphonates are a good choice to reduce the risk of serious bone fractures. We believe there has not been enough study on this group of drugs and that we are seeing the results among the 10 million Americans with osteoporosis who are taking bisphosphonates.

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