What Drugs Are Used to Strengthen Bones?

Worldwide, osteoporosis is the most common bone disease, leading to a high risk of fractures. To combat this, a variety of medications are used to strengthen bones, each working through different mechanisms to either slow bone loss or stimulate new bone formation. The best choice depends on individual health factors, fracture risk, and treatment goals.

Quick Summary

Medications for strengthening bones are categorized as antiresorptives, which reduce bone breakdown, and anabolics, which build new bone. Common drugs include bisphosphonates, denosumab, and parathyroid hormone analogs, which are chosen based on a patient's condition and risk profile.

Key Points

• Drug Categories: Bone-strengthening drugs are classified as either antiresorptive (slowing bone breakdown) or anabolic (building new bone).

• Bisphosphonates are First-Line: Medications like Alendronate, Risedronate, Ibandronate, and Zoledronic acid are common first-choice treatments, available orally or via injection.

• Denosumab for Specific Cases: This injectable drug is an alternative for patients who cannot tolerate bisphosphonates or have reduced kidney function.

• Anabolics for Severe Osteoporosis: Powerful agents such as Teriparatide, Abaloparatide, and Romosozumab are used for severe cases and actively promote bone formation.

• Supplements are Foundational: Calcium and vitamin D are crucial for overall bone health and are necessary alongside most prescription therapies.

• Treatment Choice is Personalized: The best medication depends on a patient's individual risk factors, tolerance to medication, and severity of bone loss.

• Medications Have Side Effects: All bone-strengthening drugs have potential side effects, from common GI issues to rare but serious complications like ONJ or atypical fractures.

Understanding the Bone Remodeling Process

To understand how bone-strengthening medications work, it helps to know how bones are maintained. Throughout life, bone tissue is constantly being broken down and rebuilt in a process called remodeling. This balance is maintained by two types of cells: osteoclasts, which break down old bone (resorption), and osteoblasts, which form new bone. In conditions like osteoporosis, this balance is disrupted, with bone resorption outpacing bone formation, leading to low bone mass and increased fracture risk. Medications intervene to restore this balance and strengthen bones.

Types of Bone-Strengthening Medications

Medications for bone health can be broadly classified into two groups based on their mechanism of action: antiresorptive and anabolic agents.

Antiresorptive Medications

These drugs work by slowing down bone resorption, allowing osteoblasts to catch up and rebuild bone mass. They are the most commonly prescribed type of medication for osteoporosis.

Bisphosphonates

This is the most widely used class of drugs for osteoporosis. They bind to the surfaces of bone, particularly where active resorption is occurring. When osteoclasts absorb the drug, their function is impaired, and they undergo apoptosis (programmed cell death), which reduces the rate of bone breakdown.

Common Bisphosphonates:

• Alendronate (Fosamax, Binosto): Available as a weekly oral tablet.
• Risedronate (Actonel, Atelvia): Available in weekly or monthly oral forms.
• Ibandronate (Boniva): Available as a monthly oral tablet or a quarterly intravenous (IV) infusion.
• Zoledronic Acid (Reclast): Administered as an annual IV infusion and can be an option for those who cannot tolerate oral bisphosphonates.

Side Effects and Considerations:

• Oral bisphosphonates can cause gastrointestinal issues like heartburn and nausea.
• Rare, but serious, side effects include osteonecrosis of the jaw (ONJ) and atypical femoral fractures.
• IV forms can cause flu-like symptoms after the first infusion.

Denosumab (Prolia)

Denosumab is a monoclonal antibody administered via a subcutaneous injection every six months. It works by inhibiting RANKL, a protein that is essential for the formation and function of osteoclasts. This mechanism results in a significant reduction in bone resorption and an increase in bone density.

Key Facts:

• Often used for patients who cannot take bisphosphonates.
• Requires careful monitoring of calcium levels.
• Stopping denosumab abruptly can lead to a high risk of spinal fractures, requiring follow-up therapy.
• Also carries a rare risk of ONJ and atypical fractures.

Selective Estrogen Receptor Modulators (SERMs)

SERMs, such as raloxifene (Evista), mimic the beneficial effects of estrogen on bone density in postmenopausal women without stimulating breast or uterine tissue.

Key Facts:

• Increases bone density and reduces the risk of spinal fractures.
• Can also reduce the risk of invasive breast cancer.
• Potential side effects include hot flashes and an increased risk of blood clots.

Anabolic Medications

Unlike antiresorptive drugs, these agents actively stimulate new bone formation, making them highly potent. They are typically reserved for patients with severe osteoporosis or a very high risk of fracture.

Parathyroid Hormone (PTH) Analogs

These drugs are synthetic versions of parathyroid hormone that stimulate osteoblasts to build new bone.

Common PTH Analogs:

• Teriparatide (Forteo, Bonsity): A daily self-administered injection used for a maximum of two years.
• Abaloparatide (Tymlos): Another daily injectable option, also limited to two years of use.

Key Facts:

• Leads to substantial increases in bone density and strength.
• After completing the two-year course, patients need to transition to another osteoporosis medication to maintain the new bone growth.
• Common side effects include dizziness, nausea, and leg cramps.

Romosozumab (Evenity)

This is a newer anabolic agent that is a monoclonal antibody against sclerostin, a protein that inhibits bone formation. It works by both increasing bone formation and decreasing bone resorption.

Key Facts:

• Administered as a monthly injection for a maximum of one year.
• Includes a boxed warning for a potential increased risk of cardiovascular events, including heart attack and stroke.
• Follow-up antiresorptive therapy is needed to preserve the benefits.

The Role of Supplements

While not drugs in the same category, calcium and vitamin D are essential for bone health and are often used in conjunction with prescription medications. Vitamin D helps the body absorb calcium from the diet. Adequate intake is crucial for any bone-strengthening treatment to be effective.

Comparison of Bone-Strengthening Medications

Feature	Bisphosphonates	Denosumab	Anabolic Agents	SERMs (Raloxifene)
Mechanism	Inhibits osteoclasts	Inhibits osteoclast maturation	Stimulates osteoblasts	Mimics estrogen in bone
Route of Admin.	Oral (daily, weekly, monthly) or IV (quarterly, annual)	Subcutaneous injection every 6 months	Subcutaneous daily or monthly injection	Oral (daily)
Duration	5+ years, often with drug holiday	Continuous, as stopping risks fractures	1-2 years max	Long-term use possible
Key Side Effects	GI issues (oral), flu-like symptoms (IV), rare ONJ/femur fractures	Hypocalcemia, rare ONJ/femur fractures, rebound fractures on discontinuation	Nausea, dizziness, leg cramps, hypercalcemia (PTH analogs), CV risk (Romosozumab)	Hot flashes, leg cramps, increased risk of blood clots
Best For	First-line therapy for many with high fracture risk	Patients unable to tolerate bisphosphonates, or with renal issues	Severe osteoporosis, high fracture risk	Postmenopausal women with spinal fracture risk

Conclusion

Deciding what drugs are used to strengthen bones is a complex process tailored to each patient. The choice between antiresorptive agents that slow bone loss and anabolic agents that build new bone depends on the severity of bone loss, fracture history, and individual risk factors. Bisphosphonates and denosumab are effective antiresorptive options, while newer anabolics like teriparatide, abaloparatide, and romosozumab offer powerful bone-building action for more severe cases. It is essential to discuss all options with a healthcare provider to find the most appropriate treatment plan, which will almost always include adequate intake of calcium and vitamin D.

For more information on bone health and medication options, visit the Bone Health & Osteoporosis Foundation.

Frequently Asked Questions

What is the most common first-line drug for strengthening bones?

Bisphosphonates are typically the first-choice medication for strengthening bones in patients at increased risk of fracture due to osteoporosis.

How do anabolic drugs like Forteo and Tymlos work?

Anabolic drugs like Forteo (teriparatide) and Tymlos (abaloparatide) are synthetic versions of parathyroid hormone that stimulate the body's osteoblasts to build new bone, increasing bone density.

Are calcium and vitamin D supplements enough to strengthen bones?

For most community-dwelling adults, supplements alone are not sufficient to prevent fractures and should not be used as the sole treatment for osteoporosis. They are, however, a critical part of supporting the effectiveness of prescription medications.

What is osteonecrosis of the jaw (ONJ) and which medications are associated with it?

ONJ is a rare side effect involving delayed healing of the jawbone, typically after an invasive dental procedure. It is associated with both bisphosphonates and denosumab, although it is more common with high-dose use for cancer treatment.

How is denosumab (Prolia) different from bisphosphonates?

Denosumab is a monoclonal antibody that is administered via a subcutaneous injection twice a year and works by preventing osteoclast maturation. Bisphosphonates are typically taken orally or via IV and work by inducing osteoclast apoptosis. A key difference is the risk of rebound fractures if denosumab is stopped abruptly.

How long do you need to take medication to strengthen bones?

The duration depends on the specific drug. Bisphosphonates are often taken for 5+ years, possibly followed by a 'drug holiday'. Anabolic agents are limited to 1-2 years of use. Denosumab requires continuous treatment, as stopping it can increase fracture risk.

What are the risks of taking anabolic agents like Romosozumab?

Romosozumab carries a boxed warning regarding a potential increased risk of cardiovascular events, including heart attack, stroke, and cardiovascular death. It is also limited to one year of use.