Epilepsy drugs linked to more broken bones

NEW YORK (Reuters Health) - Older adults on certain epilepsy drugs have an increased risk of breaking their wrist, hip or spine, according to a new Canadian study.

The drugs have been suspected of weakening bones for years, researchers say, but whether individual medications are different hadn’t been clear.

The Canadian team found patients on all but one of 15 common epilepsy drugs studied had higher odds of breaking a bone, with increases ranging from 25 percent to nearly 200 percent higher than people not taking the drugs.

While the study didn’t give absolute risks, in general about a third of women and a fifth of men over 50 suffer fractures related to bone thinning, or osteoporosis, according to the International Osteoporosis Foundation.

Lead researcher Dr. Nathalie Jette, of the University of Calgary in Alberta, advised that older adults on epilepsy medicine try to boost their bone health.

For instance, she said, they could stop smoking, cut back on drinking, exercise more and take calcium and vitamin D supplements.

Still, the researchers caution that they can’t be sure exactly why people taking the drugs have weaker bones.

“This study does not confirm that anti-epileptic drugs cause fracture,” Jette told Reuters Health in an e-mail.

The study is based on more than 15,000 adults aged 50 and older, who had broken their wrist, hip or spine, and more than 47,000 control subjects without fractures.

Between 2 percent and 5 percent of those people took epilepsy drugs, including carbamazepine (Tegretol), clonazepam (Klonopin), gabapentin (Neurontin), phenobarbital (Luminal), phenytoin (Dilantin) and valproic acid (Depakote).

The chances of breaking a bone were greatest for patients on phenytoin and carbamazepine, while valproic acid was the only drug not linked to an increased risk, report the researchers in the Archives of Neurology.

These differences held after taking into account other factors such as income, the use of home care and other medical conditions including diabetes. The average fracture risks were highest among patients taking more than one of the drugs.

How anti-epileptic drugs would make older bones more brittle is unclear. The researchers say it’s possible they could influence the body’s use of vitamin D or the absorption of calcium.

SOURCE: Archives of Neurology, January 2011.