Osteoporosis occurs when old bone breaks down faster than new bone is formed. Treatments for osteoporosis—such as Fosamax (alendronate), Actonel (risedronate), Evista (raloxifene), and hormone replacement therapy—all slow bone loss by reducing the rate at which bone breaks down. But another way to treat osteoporosis is to stimulate the formation of new bone. Researchers have worked for many years on the development of such a treatment, and the result is Forteo (teriparatide). Approved by the U.S. Food and Drug Administration in 2002, Forteo requires daily injections and is recommended for people with osteoporosis who are at high risk for fractures.
How Does Forteo Work?
Forteo contains the active portion of parathyroid hormone, a substance naturally produced by the body and involved in the maintenance of calcium and phosphorus levels. When given once a day, Forteo stimulates the growth of new bone by increasing the number and activity of bone-forming cells called osteoblasts. As a result, bone mass and bone strength increase.
How Well Does Forteo Work?
Clinical trials show that Forteo increases bone mineral density (BMD) and lowers the risk of fractures in postmenopausal women with osteoporosis. In a randomized trial of 1,637 postmenopausal women with prior vertebral fractures, published in The New England Journal of Medicine, women who took Forteo for a median of 19 months had a 65% lower risk of new vertebral fractures and a 53% lower risk of new nonvertebral fractures, compared with women who received a placebo. In addition, Forteo increased BMD by nine more percentage points in the spine and three more percentage points in the hip than did the placebo.
According to a study in the Journal of Bone and Mineral Research, Forteo is also effective in increasing BMD in men with osteoporosis. The effect of Forteo on fracture risk in men has not been studied.
One study has directly compared Forteo with other treatments for osteoporosis. In that study, 146 postmenopausal women with osteoporosis were randomized to receive Forteo or Fosamax. After a year, participants taking Forteo had an increase in spine BMD that was 8% greater than that of the Fosamax group. In addition, a smaller percentage of Forteo patients had nonvertebral fractures than did Fosamax patients (4% vs. 14%). The results were published in The Journal of Clinical Endocrinology and Metabolism.
What Are the Side Effects of Forteo treatment?
In clinical trials, the side effects of Forteo were usually mild, and those that occurred more often in people taking Forteo than the placebo included dizziness (8%) and leg cramps (3%). In preclinical trials, some rats given Forteo at high doses for two years developed osteosarcoma (a rare form of bone cancer). So far, no cases of osteosarcoma have been seen in humans taking Forteo. Noevertheless, people who are at increased risk for bone cncer should not use Forteo.
To be safe, people at elevated risk for osteosarcoma—people with Paget’s disease, those with unexplained elevations of alkaline phosphatase, those who’ve had radiation to the bones, or those with cancer that has spread to the bones—should not take Forteo.
Another possible serious side effect of Forteo is elevated blood calcium levels (hypercalcemia). Signs of hypercalcemia include confusion, muscle or bone pain, nausea, vomiting, and a slow or irregular heartbeat. If you experience any of these symptoms, contact your doctor.
Who Should Take Forteo?
Forteo should be used only in men and postmenopausal women who have osteoporosis and are at high risk for fractures. This includes people who have had fractures in the past, have multiple risk factors for fracture (for example, very low BMD and frequent falls), or have not responded to or cannot take other osteoporosis treatments. Forteo should not be used for the prevention of osteoporosis.
People who should not take Forteo include children, women who are pregnant or breast-feeding, people at risk for osteosarcoma (see above), those with a bone disease other than osteoporosis, those with cancer that has spread to the bone, and those with high blood calcium levels. Forteo should be used with caution in people taking digitalis.
How To Take Forteo
The daily dosage of Forteo is 20 micrograms (mcg). Taking the dose involves giving yourself an injection of the medication under the skin of your thigh or abdomen each day using a pen device. Your health care professional will teach you how to do this.
You can take Forteo at any time of the day and with or without food or drink. The first few times you use it, you may feel lightheaded or have heart palpitations. Sitting or lying down will relieve these symptoms. Since the safety of Forteo has not been evaluated beyond two years, the drug should not be used for longer than this period.
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