SAN FRANCISCO — Bisphosphonates remain the prime oral therapies for osteoporosis, but some competing agents might alter medical practice, Dr. Steven T. Harris said at a meeting on diabetes and endocrinology that was sponsored by the University of California, San Francisco.
More liberal use of vitamin D and a new indication for the selective estrogen receptor modifier raloxifene (Evista) give these agents a higher clinical profile, said Dr. Harris of the university. Investigational oral therapies that soon are likely to play a role in osteoporosis treatment include the monoclonal antibody denosumab and the new bisphosphonate zoledronic acid (Reclast).
▸ Vitamin D. Institute of Medicine recommendations in 1997 that adults get 200–600 IU a day of vitamin D (depending on age) now are widely considered to be inadequate. The minimum probably should be 800–1,000 IU a day for adults, and it's almost impossible to overdose on vitamin D, he noted.
Experts have urged clinicians to keep patients' 25-hydroxyvitamin D levels up to 30 ng/mL or higher, so “we ought to be a little more generous in our D supplementation than we have been historically,” he said.
Multiple studies in recent years have reported associations between vitamin D insufficiency and an increase in a variety of immune diseases and malignancies including osteoarthritis, multiple sclerosis, fibromyalgia, type 1 diabetes, and cardiovascular disease.
Dr. Harris changed his practice toward greater emphasis on vitamin D supplementation after a recent study showed that half of osteoporotic patients on prescription therapies had vitamin D insufficiency regardless of where they lived (J. Clin. Endocrinol. Metab. 2005;90:3215–24).
▸ Raloxifene. Approved for the prevention or treatment of osteoporosis, raloxifene has been shown to decrease the incidence of vertebral fractures in women with preexisting vertebral fractures or low bone density. It does not affect the risk of nonvertebral or hip fractures and so “does not compete terribly well with other osteoporosis treatment options,” Dr. Harris said.
Three other studies report that raloxifene decreases the risk of estrogen receptor-positive invasive breast cancer (but not estrogen receptor-negative tumors or ductal carcinoma in situ). “It's almost certain that sometime this year Evista is going to be approved by the Food and Drug Administration to reduce the risk of breast cancer.”
That added indication might boost raloxifene's use for some osteoporotic patients, though that remains to be seen.
▸ Denosumab. One subcutaneous injection of this experimental monoclonal antibody greatly decreases bone resorption almost immediately, a recent study suggests. One injection every 6 months produced bone density improvements similar to gains seen in patients treated weekly with the oral bisphosphonate alendronate (N. Engl. J. Med. 2006;354:821–31).
A large clinical trial is studying denosumab for osteoporosis. No data on fracture prevention are available yet.
▸ Zoledronic acid. A 15-minute intravenous infusion of 5 mg zoledronic acid once yearly for 3 years in lieu of oral therapy significantly reduced vertebral, nonvertebral, and hip fractures in a study of 7,736 postmenopausal women randomized to the drug or placebo, according to preliminary results reported at a 2006 conference. Zoledronic acid is not approved to treat osteoporosis but is indicated for treatment of patients with hypercalcemia of malignancy, multiple myeloma, Paget's disease of bone, or bone metastases from solid tumors. Dr. Harris predicted the drug would win approval for osteoporosis, and he said he believes it is unlikely to prove more effective than oral therapies but could offer an alternative for osteoporotic patients who can't or won't take oral medication.
'We ought to be a little more generous in our D supplementation.' DR. HARRIS