US guidelines recommend pharmacologic therapy for postmenopausal women with a bone density T-score (standard deviation from normal mean values in healthy young women) of -2.5 or below in the lumbar spine, femoral neck, total hip, or distal radius, a T-score between -1.0 and -2.5 and a history of fragility (low-trauma) fracture of the hip or spine, or a T-score between -1.0 and -2.5 and a FRAX 10-year probability of ≥3% for hip fracture or ≥20% for major osteoporotic fracture (hip, clinical spine, humerus, distal radius).

View the Comparison Table: Some Drugs for Postmenopausal Osteoporosis

The FDA has approved romosozumab-aqqg (Evenity – Amgen), a sclerostin inhibitor, for once-monthly subcutaneous (SC) treatment of osteoporosis in postmenopausal women who are at high risk for fracture (history of osteoporotic fracture or multiple risk factors for fracture) or who have failed or cannot tolerate other drugs for this indication. Romosozumab is the first sclerostin inhibitor to be approved in the US and the third drug for treatment of postmenopausal osteoporosis that stimulates bone formation; the parathyroid hormone (PTH) receptor agonists abaloparatide (Tymlos) and teriparatide (Forteo) were approved earlier. Other drugs used for treatment of postmenopausal osteoporosis, such as bisphosphonates, inhibit bone resorption and decrease bone turnover.

View the Comparison Table: Drugs for Postmenopausal Osteoporosis

View the Comparison Table: Drugs for Postmenopausal Osteoporosis

US guidelines for the treatment of osteoporosis have been published. The diagnosis of osteoporosis has traditionally been established by the occurrence of fragility fractures or by bone densitometry, which is generally reported in terms of standard deviations (SD) from mean values in young adults (T-score). The World Health Organization (WHO) has defined normal bone mineral density (BMD) for women as a value within one SD of the young adult mean. Values 2.5 SD or more below the mean (T-score -2.5 or below) at the spine, femoral neck, or total hip are defined as osteoporosis. The WHO has developed a computerized model (FRAX) that predicts the 10-year probability of a hip fracture or other major osteoporotic fracture based on clinical risk factors and BMD at the femoral neck.

Osteoporosis is characterized by low bone mass with microarchitectural disruption and skeletal fragility that results in an increased risk of fracture. The diagnosis has traditionally been established by bone densitometry, which is generally reported in terms of standard deviations (SD) from mean values in young adults (T-score). The World Health Organization (WHO) has defined normal bone mineral density (BMD) for women as a value within one SD of the young adult mean. Values 2.5 SD or more below the mean (T score -2.5) are defined as osteoporosis. The WHO has developed a computerized model (FRAX) that predicts the 10-year probability of a hip fracture or any other major osteoporotic fracture based on clinical risk factors and BMD at the femoral neck.

The FDA and two of its advisory committees have been debating whether to recommend limiting the duration of use of bisphosphonates in order to prevent atypical femoral fractures and possibly other side effects of the drugs. The agency produced a 182-page background document on this subject for a joint meeting of the Reproductive Health Drugs and the Drug Safety and Risk Management Advisory Committees held on September 9, 2011 (www.fda.gov). The document concluded that there is no clear evidence, with regard to fractures, of benefit or harm in continuing the drugs beyond 3-5 years. The two advisory committees recommended that the labels for these drugs clarify their duration of use; they did not specify what that duration should be. A Treatment Guidelines from The Medical Letter issue on Drugs for Postmenopausal Osteoporosis will be published in November.

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The In-Brief article on delayed-release risedronate in issue 1360 (Med Lett Drugs Ther 2011; 53:24) included a statement that alendronate is currently the only bisphosphonate available generically. That would have been accurate if we had added "that is FDA-approved for treatment of osteoporosis." Etidronate (Didronel, and others), which was the first bisphosphonate used to treat osteoporosis (Medical Letter 1990; 32:111) but was never approved for such use by the FDA, is also available generically. It is approved for treatment of Paget's disease and for prevention and treatment of heterotropic ossification following hip replacement and in spinal-cord injured patients.

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A new enteric-coated delayed-release formulation of risedronate (Atelvia – Warner Chilcott) has been approved by the FDA for treatment of postmenopausal osteoporosis. Unlike immediate-release risedronate (Actonel) and all other oral bisphosphonates, which must be taken after an overnight fast and at least 30 minutes before eating breakfast, the new formulation is taken immediately after breakfast with at least 4 ounces of water. Then the patient must remain upright for at least 30 minutes.

CLINICAL TRIAL — Approval of Atelvia was based on a 52-week non-inferiority study in more than 900 postmenopausal women comparing the new 35-mg delayed-release tablet taken once each week to the original immediate-release 5-mg tablet taken daily at least 30 minutes before breakfast. (FDA approval of risedronate was based on studies with the 5-mg tablet taken once daily; now Actonel is usually taken, like Atelvia, as a 35-mg tablet once a week.) Increases in bone mineral density at the lumbar spine and other locations and changes in markers of bone turnover were similar in both groups. Diarrhea and abdominal pain occurred more frequently with the new formulation once weekly after breakfast than with risedronate 5 mg daily (8.8% vs. 4.9% and 5.2% vs. 2.9%, respectively).1

DOSAGE AND COST — Atelvia is available as a 35-mg tablet taken once each week. A month’s supply of the new formulation (four 35-mg tablets) costs $119.99, which is similar to the cost of Actonel once a week ($126.47).2 Alendronate (Fosamax, and others) is currently the only bisphosphonate available generically that is FDA-approved for treatment of osteoporosis; a month’s supply is available at some discount pharmacies for $9.

CONCLUSION — Taking the new enteric-coated delayed-release formulation of risedronate (Atelvia) after breakfast presumably would be more convenient than taking immediate-release risedronate 30 minutes before breakfast, but it may cause more diarrhea. Generic alendronate costs much less than either one.

1. MR McClung et al. BMD response to delayed-release risedronate 35 mg once-a-week formulation taken with or without breakfast. J Clin Densitom 2010; 13:132; Poster number 067.

2. Cost at drugstore.com. Accessed March 14, 2011.

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