Osteoporosis Medications Explained
Marc Hochberg, MD, MPH, MACP, President, USBJI
In my message published in March 2018, I discussed the increasing burden of osteoporosis and related fractures in the United States and highlighted several recent publications. In addition, I mentioned the involvement of the USBJI in the “Strategic Roadmap to Prevent Secondary Fractures” sponsored by the American Society for Bone and Mineral Research. A key part of the strategy is the use of drugs approved by the U.S. Food and Drug Administration for the treatment of patients with osteoporosis to prevent fractures, especially those affecting the spine and hip.
Osteoporosis is a disease in which the mass, density and quality of bone are reduced leading to an increased risk for fracture. In the majority of postmenopausal women and older men with osteoporosis, the cause is an imbalance between rates of bone formation and bone resorption. The former is accomplished by cells called osteoblasts which make the bone matrix and mineralize the matrix. The latter is accomplished by cells called osteoclasts which produce enzymes that degrade and resorb the bone matrix. Bone mass is maintained in the adult by a synchronized process called bone remodeling; osteoporosis is usually due to bone loss due to an excess rate of bone resorption compared to bone formation.
The most common approach to initial drug treatment for patients with osteoporosis is the use of anti-resorptive agents, drugs that reduce the rate of bone resorption. The most commonly used anti-resorptive agents are a class of drugs called bisphosphonates. The bisphosphonates include orally administered drugs such as alendronate and risedronate and an intravenously administered agent, zoledronic acid. Alendronate is commonly taken once weekly while risedronate can be taken either once weekly or once monthly. Zoledronic acid is administered by a licensed health care provider intravenously once yearly. Each of these agents has been shown to reduce the risk of both spine and hip fractures as well as other clinical fractures. The alternative anti-resorptive agent, usually reserved for patients with either a contraindication to or who were intolerant of a bisphosphonate, is an inhibitor of RANK-Ligand, denosumab. Denosumab is administered by a licensed health care provider as a subcutaneous injection, every six months.
An alternative approach to use of anti-resorptive agents is the administration of an anabolic agent, a drug that stimulates bone formation by the osteoblast. There are two anabolic agents approved by the FDA: teriparatide and abaloparatide. Both of these agents strongly increase the magnitude of bone mineral density and bone mass as well as reduce fracture risk. They are self-administered as a daily subcutaneous injection, like insulin.
The choice of a medication for treatment of osteoporosis involves the process of shared decision making wherein the provider recommends a specific treatment based on the benefits and risks of the agent and the patient decides based on the preference for an oral, subcutaneous or intravenous injection, taking the medication daily, weekly, monthly, semiannually or annually and concern regarding contraindications and occurrence of rare adverse events. Obviously, these decisions are best left to the individual patient and provider after discussion and review of relevant information available from patient and professional societies such as the National Osteoporosis Foundation.