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.

Diagnosis of osteoporosis is based on the results of bone mineral density (BMD) testing or by the occurrence of a fragility fracture. Bone densitometry results are generally reported in terms of standard deviations (SD) from the mean value for young adults (T-score). The World Health Organization (WHO) defines osteoporosis in women as a T-score of -2.5 or below in the spine, femoral neck, or total hip. A computerized model (FRAX) is available that estimates the 10-year probability of a hip fracture or other major osteoporotic fracture based on clinical risk factors and BMD at the femoral neck.

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.

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 FDA, which had previously approved intravenous (IV) administration of 5 mg of zoledronic acid (Reclast – Novartis) once a year for treatment of postmenopausal osteoporosis (Med Lett Drugs Ther 2007; 49:89), has now approved the same dose for use once every 2 years to prevent osteoporosis in postmenopausal women with osteopenia.

Clinical Studies – In an unpublished study summarized in the package insert, 224 women with osteopenia ≤5 years after menopause were given an IV infusion of zoledronic acid 5 mg or placebo; 2 years later, total hip bone mineral density (BMD) had increased by 2.6% with the drug and decreased by 2.1% with placebo. Among 357 osteopenic women >5 years after menopause, hip BMD 2 years after one IV dose of zoledronic acid increased by 2.1% and decreased by 1.0% with placebo. Both of these differences from placebo were statistically significant. Similarly significant increases occurred in vertebral BMD. No data are available on the incidence of hip or vertebral fractures in these women, but zoledronic acid once a year for treatment of osteoporosis has been shown to decrease the incidence of such fractures.

Adverse Effects — An acute-phase reaction including fever, flu-like symptoms, headache, arthralgia and myalgia can occur with IV administration of zoledronic acid; symptoms usually subside within a few days. Renal damage can occur after a single dose, especially with concomitant use of other nephrotoxic drugs, including nonsteroidal anti-inflammatory drugs (NSAIDs). Jaw osteonecrosis has occurred rarely. Whether long-term use of bisphosphonates, which interfere with bone remodeling, could increase the incidence of long-bone fractures remains to be established. None of these events, except for acutephase reactions, occurred during the clinical trial, according to the manufacturer.

Cost – The cost of one 5-mg injection of Reclast is about $1200 for the drug alone.

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The bisphosphonate risedronate (Actonel - Procter & Gamble) was recently approved by the FDA in a 150- mg once-monthly oral tablet for prevention and treatment of postmenopausal osteoporosis. The drug is also available for the same indication in 5-mg daily, 35-mg weekly and 75-mg twice-monthly tablets.