Pharmacologic treatment is recommended for postmenopausal women who have bone density T-scores (standard deviations from normal mean values in the spine, femoral neck, total hip, or distal radius) of -2.5 or below, T-scores between -1.0 and -2.5 with a history of fragility (low-trauma) fracture of the hip or spine, or T-scores between -1.0 and -2.5 with a FRAX 10-year probability of ≥3% for hip fracture or ≥20% for major osteoporotic fracture.

View the Comparison Table: Some Drugs for Postmenopausal Osteoporosis

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

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.

Radium Ra 223 dichloride (Xofigo – Bayer), a radiotherapeutic drug, has been approved by the FDA for intravenous treatment of castration-resistant prostate cancer with symptomatic bone metastases and no known visceral metastatic disease.

Long-term use of bisphosphonates for prevention and treatment of osteoporosis has been associated with osteonecrosis of the jaw, atypical fractures of the femur, and possibly esophageal cancer. So for how long should patients take them?

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 FDA, which recently approved subcutaneous (SC) administration of denosumab (Prolia – Amgen) for treatment of postmenopausal osteoporosis,1 has now approved the same drug with a different brand name (Xgeva – Amgen) and dosage for prevention of skeletal-related events (such as pathologic fracture, spinal cord compression or radiation to bone) in patients with bone metastases from solid tumors. Denosumab is a fully human anti-RANK ligand antibody that inhibits the formation, activation and survival of osteoclasts.2

A prospective, randomized, double-blind trial in 1901 patients with bone metastases from castration-resistant prostate cancer found that denosumab 120 mg injected SC every 4 weeks, compared to the bisphosphonate zoledronic acid (Zometa) 4 mg IV, delayed the time to a first skeletal event by 3.6 months (20.7 vs. 17.1 months).3 In 1776 patients with bone metastases from solid tumors or multiple myeloma, the mean time to a first skeletal event was 20.6 months with SC denosumab and 16.3 months with IV zoledronic acid.4

Denosumab can lower serum calcium concentrations, especially in patients with impaired renal function. Fatigue is the most commonly reported adverse effect. Other adverse effects of both denosumab and zoledronic acid in clinical trials have included nausea, dyspnea and diarrhea. Acute-phase reactions and renal toxicity have been less frequent with denosumab than with zoledronic acid. Osteonecrosis of the jaw, which can occur with bisphosphonates, has also been reported with denosumab.

1. Denosumab (Prolia) for postmenopausal osteoporosis. Med Lett Drugs Ther 2010; 52: 81.

2. A Lipton and C Goessl. Clinical development of anti-RANKL therapies for treatment and prevention of bone metastasis. Bone 2011; 48:96.

3. K Fizazi et al. A randomized phase III trial of denosumab versus zoledronic acid in patients with bone metastases from castration-resistant prostate cancer. J Clin Oncol 2010; 28:18s (abstr LBA4507).

4. D Henry et al. A double-blind, randomized study of denosumab versus zoledronic acid for the treatment of bone metastases in patients with advanced cancer (excluding breast and prostate cancer) or multiple myeloma. Eur J Cancer Suppl 2009; 7:11 (abstr 20LBA).

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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.

Zoledronic acid (Reclast - Novartis) is the first bisphosphonate approved by the FDA for once-yearly intravenous (IV) treatment of osteoporosis in postmenopausal women. Reclast is also approved for treatment of Paget's disease. Another IV formulation of zoledronic acid (Zometa) is approved for treatment of hypercalcemia of malignancy, multiple myeloma and bone metastases from solid tumors.

A 10-year study of daily oral alendronate (Fosamax) and a 7-year study of daily oral risedronate (Actonel) indicate that both drugs maintained increases in bone mineral density (BMD) and decreases in markers of bone remodeling throughout the study period. Both drugs are now more commonly taken once weekly. Available data are insufficient to compare fracture rates with alendronate and risedronate, and fracture rates are considered the most important endpoint in osteoporosis studies. Recent reports of severe pain and jaw osteonecrosis with these drugs are disturbing.