Drugs long known to contribute to Osteoporosis
It has been known for decades that certain medications can contribute to bone loss. Among these drugs are corticosteroids such as cortisone, hydrocortisone, glucocorticoids, and prednisone. These drugs are used to treat asthma, rheumatoid arthritis, psoriasis, and colitis, among other conditions. Aluminum containing antacids contribute to osteoporosis because aluminum binds to minerals and renders them useless. Prolonged thyroid hormone therapy may lead to a significant loss of calcium from bones, increasing the risk of fractures in the spine, hip, and wrists. Thyroid hormone directly affects osteoblasts, stimulating them to release cytokines that then prompt osteoclasts to break down bone.
Progestin-based contraceptives such as Depo-Provera decrease estrogen levels, thereby increasing the risk of bone loss. Certain anticoagulants (blood thinning drugs) such as heparin have been known since 1963 to contribute to osteoporosis. Immunosuppressants such as cyclosporine, tacrolimus, and methotrexate can cause osteoporosis by interfering with the function of the osteoblasts that form bone and by stimulating bone breakdown. Anticonvulsants such as Dilantin decrease the production of vitamin D and interfere with calcium absorption. Lithium, a drug used to treat manic-depressive disorder, and high-dose loop diuretics, such as Lasix, also increase the risk for bone loss.
Antidepressants and the risk of Osteoporosis
The idea that serotonin might be involved in bone came as a surprise almost a decade ago. Researchers were astonished to find serotonin transporters and receptors in the bones of mice. (Bliziotes et al, Bone, 200l and Westbroek et al, Journal of Biological Chemistry, 2001). Serotonin transporters are in all types of bone cells - osteoblasts, which build new bone; osteoclasts, which break down old bone; and osteocytes, which are cells derived from osteoblasts. Disruption of the serotonin transporter results in lower bone mass, altered bone architecture, and reduced bone strength in mice. Following the discovery of a serotonin connection to bones, researchers wondered what effect Selective Serotonin Re-Uptake Inhibitors (SSRIs) might have on bone. SSRIs are a class of antidepressants that include Prozac, Paxil, and Zoloft. The drugs work by inhibiting the protein that transports serotonin. The possibility was raised that SSRIs might affect bone density by interfering with the regular breaking down and rebuilding of bone.
Two related studies published in the June 25, 2007, issue of The Archives of Internal Medicine studied the effect of SSRIs in humans. In the first study the subjects were 2,722 women with an average age of 78. The study found that bone density declined in those taking SSRIs twice as fast as it did in other women. (Diem, et al) A similar study was done with nearly 6000 men, average age 65, with similar results. Men taking SSRIs had lower average bone density than those not on the drugs. (Haney, et al) The observed difference in bone mineral density for SSRIs was similar to that seen with glucocorticoids, the researchers said.
A third study published in the January 22 Archives of Internal Medicine, found that daily SSRI use in adults 50 years of age and older was associated with an increased risk of bone loss. The study found that those who took SSRIs had twice the fracture risk as those who did not take the medication. The risk of falling was also higher among those taking the pills, which can cause a drop in blood pressure and fainting in some people. (Goltzman, et al)
The most recent study appeared in the May 2009 issue of the Journal of General Internal Medicine. Lead researcher Leslie Spangler found that antidepressant use in postmenopausal women, who averaged 64 years of age, was linked to an increased risk of fractures of the spine and other sites. Those women on antidepressants had a 30 percent increased risk of spine fracture, she said, and a 20 percent increased risk of any type of fracture.
These studies are observational studies and therefore do not prove a cause and effect relationship between antidepressants and osteoporosis. To prove cause and effect, clinical trials are required. Observational studies can only show an association.
Next week's article will be on two other classes of drugs that cause osteoporosis.
Mary Lou Williams, M. Ed., is a lecturer and writer in the field of nutrition. She welcomes inquiries. She can be reached at 267-6480.