Side Effects of Osteoporosis Medications Like Fosamax, Boniva, and Reclast

Potential lack of efficacy is not the only reason why most people prescribed bisphosphonate drugs for osteoporosis like Fosamax, Actonel, Boniva, or Reclast may stop taking them within a year. There are two rare but devastating side effects— osteonecrosis of the jaw and atypical femur fractures—that contributed to around a 50 percent drop in the use of this class of drugs when they came to light. The New York Times article noting the decline explained the reasoning: “Reports of the drugs causing jawbones to rot and thighbones to snap in two have shaken many osteoporosis patients so much, that they say they would rather take their chances with the disease.”

The jaw-rot syndrome that prevents many from initiating treatment for fear of “their jaw falling off” can severely impact many aspects of quality of life, but is exceedingly rare, affecting at most one in a thousand patients treated for osteoporosis. Atypical femur fractures can occur more frequently, though, as many as one in 300 users treated for three years. They are called “atypical,” because they occur not after a fall or trauma, but just during routine activities, like walking, twisting at the waist, or even just standing still. Your femur, your thigh bone, the biggest bone in your body—just breaks in half. Too cruel an irony from a drug that’s supposed to protect your bones. This is what it looks like on x-ray. Ouch.

Bisphosphonates work by inhibiting the action of a type of bone cell called osteoclasts. Your entire skeleton is constantly being remodeled with bone added in some spots and taken away in others to conform to changing demands. The cells that are continually laying down new bone are called osteoblasts, and the ones that chisel away old bone are the osteoclasts. It makes sense, then, that curbing the ‘clasts would prevent bone loss. But by reducing the active remodeling process, bisphosphonates can “freeze” the skeleton, allowing for the accumulation of microcracks over time, resulting in stress fractures. Other osteoporosis drugs like Denosumab (sold, as “Prolia”) prevent the same formation of osteoclasts in the first place and have been plagued by the same kinds of rare but disturbing side effects.

As with anything in life, it all comes down to risks versus benefits. How many hip fractures are prevented for every femur that snaps? It depends on your race and how long you’re on these drugs. After five years in white women, 36 hip fractures are prevented for every atypical femur fracture. Hispanic women only get half the benefit, about 18 to 1, and for Asian women, it’s only about 5 hip fractures prevented for every femur fracture caused. (The study claims it failed to accrue enough data on Black women.) At ten years of drug exposure, the ratios get worse, 16:1 for white women, 5:1 for Hispanic women, and only 1.5:1 for Asian women, meaning that the devastating fractures prevented and caused in Asian women are nearly comparable.

A nationwide survey of resident physicians found that knowledge regarding osteoporosis diagnosis and treatment was poor, with a particularly striking lack of knowledge regarding the two serious drug side effects. The good news is that after stopping the drugs, the risk of femur fracture rapidly drops by 70 percent within a year, leading to the suggestion that a drug “holiday” be considered after a few years on the drug to help mediate the risk.