What do bone-loss medications (bisphosphonates) do, and are they safe?

Bisphosphonates work by causing the cells that break down bone -- the osteoclasts -- to die off. The drugs bind to bone mineral, are taken up by those breakdown cells, and trigger a kind of self-destruction within them. This shifts the balance: your bones lose less mass.

That this also genuinely prevents fractures is well established. In people with osteoporosis the benefit-to-risk ratio is favourable, especially when fracture risk is high. And that risk is serious: international research across 19 countries shows that 14 to 28 percent of patients die within a year after a hip fracture. Preventing that first fracture therefore makes a real difference.

Are you taking prednisone or other corticosteroids long-term? If so, these drugs significantly weaken your bones. In that case, oral bisphosphonates are the first choice, preferably combined with vitamin D and calcium. Bone density demonstrably increases, although the evidence that this directly leads to fewer fractures in this specific group is somewhat less complete than for ordinary osteoporosis.

One peculiarity of these drugs is that the effect does not stop as soon as you discontinue them. They remain bound to your bone mineral for years and are released gradually. As a result, the protection persists for some time after stopping. This is different from drugs such as denosumab, where the protective effect disappears quickly after discontinuation.

The best-known serious side effect is osteonecrosis of the jaw: bone tissue in the jaw that dies off. This is rare, but the risk is considerably higher in cancer patients receiving high doses via infusion than in osteoporosis patients taking low oral doses. A dental visit before starting treatment and good oral hygiene during treatment are routinely recommended. Even so, internationally only 11 to 50 percent of patients who have had a hip fracture actually receive preventive medication -- men even less often than women.