Daily antidepressant use doubled the risk of bone fractures in older adults, researchers reported Monday, raising new safety concerns about the widely prescribed drugs.
The study published in Archives of Internal Medicine found that about 10 percent of daily antidepressant users older than age 50 fractured a bone over a five-year period. Among people who did not use antidepressants, the fracture rate was 5 percent.
Researchers said patients on antidepressants should be aware of the risks but should not stop taking their drugs because of worries about bone fractures.
Dr. Michael Bliziotes of Oregon Health & Science University, who is conducting similar research, said it was important for such patients to receive adequate calcium and exercise to maintain health bones.
"What this study points to is a need for heightened surveillance of these people," Bliziotes said.
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The study, led by researchers at McGill University in Montreal, focused on a class of antidepressants known as selective serotonin reuptake inhibitors, or SSRIs. U.S. sales of the drugs, which include Prozac and Zoloft, totaled $10.9 billion in 2004, according to the report.
The medications are prescribed for a range of mood disorders and behaviors, including anxiety, depression and eating disorders. Last month, a federal advisory committee warned of a risk of suicidal thinking in young adults taking the drugs.
The latest study was part of the Canadian Multicenter Osteoporosis Study, a 10-year, 5,000-patient trial funded by the Canadian government, several companies that market osteoporosis drugs and Eli Lilly & Co., the maker of Prozac.
SSRIs were used daily by 137 people, or 2 percent of trial participants. McGill's Dr. David Goltzman, senior author of the study, said the prevalence of antidepressant use was the same in the general population.
The study found that patients on antidepressants were twice as likely to fall and had lower bone mineral density at the hip and spine. Goltzman said it was likely the falls were caused by low blood pressure and fainting spells, two known side effects of SSRIs.
The study took into account the increased falls and lower bone density, but still found a doubling of the risk for bone breakage, Goltzman said.
He said SSRIs appear to not only reduce bone thickness but also bone strength.
"If you have two structures of the same thickness, and one is concrete and the other is glass, the glass will shatter more readily," he said.
