How do the bone-strengthening medications work?

Gabe Mirkin, M.D.

Your bones change all the time. Every day, certain bone cells called osteoblasts bring calcium into bones to make them stronger. Other cells called osteoclasts carry calcium out of bone which makes them weaker. Your bones are strongest when you are 20 years old. As you age, the osteoclasts do more work than the osteoblasts, so most people spend their entire lifetimes losing calcium from bones.

Some people get so osteoporotic that they break their bones with slight trauma and can die from the complications. You are at increased risk for osteoporosis if you are thin, have blond hair or blue eyes, drink more than two drinks a day, smoke, do not exercise, eat huge amounts of meat, or are a woman who goes into menopause before age 52.

You can help to prevent or treat osteoporosis by lifting heavy weights, which increases the effect of osteoblasts strengthening bones. Bisphosphonates such as Fosamax block osteoclasts from taking calcium out of bones, while they leave osteoblasts alone, for a net gain of calcium taken in bones. The first large, long-term study of Fosamax, published in the New England Journal of Medicine (March 11, 2004) showed continuing bone-strengthening benefits after ten years with no significant side effects.

January 8, 2006