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

Bisphosphonates inhibit the cells that break down bone. Those cells absorb the drug from the bone tissue to which it has attached, after which they die. The result: bone resorption decreases sharply, bone mineral density rises, and the number of fractures demonstrably falls in people with osteoporosis. This has been robustly shown in multiple studies, and at high fracture risk the benefit outweighs the risks for treatment durations of up to ten years.

The best-known side-effect risk is osteonecrosis of the jaw: a condition in which a piece of jawbone dies and no longer heals. This is a recognised drawback, although the precise cause has not yet been fully explained. The anatomy of the jaw and bacteria in the oral cavity are both thought to play a role. People who use bisphosphonates would therefore be wise to discuss any dental procedures in advance with their treating physician.

A practical advantage of bisphosphonates over other bone medications is that they remain stored in the bone for a long time. The effect therefore disappears gradually after stopping, rather than abruptly. With certain other drugs, such as denosumab, this is different: the effect diminishes quickly once treatment stops, which can create an additional risk of fractures during the transition period.

Despite the evidence for effectiveness, the large majority of patients receive no treatment for osteoporosis after a hip fracture. An international study covering more than four million hip fractures in nineteen countries found that only eleven to fifty percent of patients received medication afterwards. Men were prescribed treatment even less often than women, while their chance of dying within a year after a hip fracture was actually higher. That mortality varies internationally from fourteen to nearly thirty percent. This shows that undertreatment is a large, solvable problem.