Management of Osteoporosis

Definition and Diagnostic Threshold

Goals of Management

1. Prevent fragility fractures (hip, vertebral, wrist)
2. Slow or reverse progressive bone loss
3. Reduce pain and disability
4. Address underlying causes (secondary osteoporosis)

I. Non-Pharmacological (Lifestyle) Management

• Calcium intake: Adequate dietary calcium (dairy, leafy greens) is first-line therapy; supplements used when dietary intake is insufficient (1000-1200 mg/day in postmenopausal women)
• Vitamin D: Supplementation maintains calcium absorption and bone mineralization (800-1000 IU/day recommended)
• Weight-bearing exercise: Walking, resistance training, and high-impact exercise throughout life stimulate bone formation and improve muscle strength, reducing fall risk
• Fall prevention: Home safety modifications, balance training, avoiding sedative medications
• Smoking cessation: Smoking accelerates bone loss
• Limit alcohol: Excess alcohol is an independent risk factor
• Avoid prolonged glucocorticoid use where possible (glucocorticoids at ≥5 mg/day for >3 months are a major secondary cause)
• Textbook of Family Medicine 9e, p. 1062

II. Pharmacological Management

Who to Treat?

• T-score ≤ -2.5 (osteoporosis)
• History of fragility fracture (regardless of T-score)
• Osteopenia (T-score -1.0 to -2.5) plus high fracture risk by FRAX: 10-year hip fracture risk ≥3% or major osteoporotic fracture risk ≥20%

A. Antiresorptive Agents

1. Bisphosphonates (First-Line)

• Esophagitis / esophageal ulcers (oral agents) - patient must remain upright for 30-60 minutes after taking, with a full glass of water on an empty stomach
• Osteonecrosis of the jaw (ONJ): rare but serious, more common with prolonged use
• Atypical femur fractures: rare, with long-term use
• Acute-phase reaction: flu-like symptoms with IV zoledronic acid (first dose)

2. Denosumab (First-Line Alternative)

• Human monoclonal antibody that inhibits RANKL (receptor activator of nuclear factor-κB ligand)
• Blocks osteoclast formation, function, and survival
• Dose: 60 mg subcutaneous injection every 6 months
• Particularly useful in patients with renal impairment (where bisphosphonates are contraindicated) or at higher fracture risk
• Important caveat: Unlike bisphosphonates, stopping denosumab causes a rebound surge in bone resorption; must transition to a bisphosphonate when discontinuing
• Katzung's Basic and Clinical Pharmacology 16e, p. 1216

3. Selective Estrogen Receptor Modulators (SERMs) - Second Line

• Raloxifene: First SERM approved for osteoporosis prevention/treatment
• Acts as estrogen agonist on bone, antagonist on breast and uterine tissue
• Reduces vertebral fracture risk but not hip fracture
• Also reduces risk of ER+ breast cancer (added benefit)
• Not as potent as bisphosphonates for bone density
• Katzung's Basic and Clinical Pharmacology 16e, p. 1216

4. Calcitonin - Third / Last Line

• Inhibits osteoclast activity
• Mainly used for pain relief in acute vertebral fractures
• Less effective than bisphosphonates; reserved as last-line option (SOR: C)
• Textbook of Family Medicine 9e, p. 1062

5. Hormone Replacement Therapy (HRT/Estrogen)

• Proven efficacy in preventing postmenopausal osteoporosis
• No longer first-line due to increased risks of breast cancer, cardiovascular disease, and thromboembolic events (WHI trial data)
• May be considered in recently menopausal women with vasomotor symptoms where benefits outweigh risks
• Textbook of Family Medicine 9e, p. 1062

B. Anabolic Agents (Bone Formation Stimulators)

1. Teriparatide (PTH 1-34)

• Recombinant parathyroid hormone analog
• Acts as PTH receptor agonist - stimulates osteoblast activity and new bone formation
• Dose: 20 mcg subcutaneous daily
• Duration: Limited to 2 years (risk of osteosarcoma in animal studies)
• After stopping, must follow with antiresorptive therapy to maintain gains

2. Abaloparatide (PTHrP analog)

• PTH-related protein analog with similar anabolic mechanism to teriparatide
• Dose: 80 mcg subcutaneous daily
• Also limited to 2 years

3. Romosozumab (Sclerostin Inhibitor)

• Monoclonal antibody against sclerostin, a Wnt signaling inhibitor
• Dual mechanism: promotes osteoblast activity (anabolic) AND reduces osteoclast activity (antiresorptive)
• Dose: Monthly subcutaneous injection for 12 months only
• Followed by antiresorptive therapy
• Caution: Contraindicated in patients with recent MI or stroke (cardiovascular signal)
• Lippincott Illustrated Reviews: Pharmacology, p. 900

III. Sequential Therapy Strategy

• Severe/very high risk: Start with anabolic agent (teriparatide or romosozumab) THEN transition to antiresorptive (bisphosphonate or denosumab) to consolidate gains
• Moderate risk: Start with antiresorptive (bisphosphonate or denosumab) directly
• After denosumab discontinuation: Always bridge to bisphosphonate to prevent rebound bone loss

IV. Monitoring

• Repeat DXA scan every 1-3 years after initiating therapy
• Bone turnover markers (CTX, P1NP) can assess early treatment response
• Reassess fracture risk at each visit
• Screen for and treat secondary causes (vitamin D deficiency, hyperparathyroidism, hypogonadism, thyroid disease)

V. Special Populations

• Goldman-Cecil Medicine, p. 857; Berek & Novak's Gynecology, p. 944

Summary Table: Drug Classes at a Glance

Bisphosphonates in Osteoporosis - Short Note

Introduction

Classification and Available Agents

Mechanism of Action

• Protein prenylation (geranylgeranylation)
• Osteoclast cytoskeletal function and ruffled border formation
• Osteoclast survival signaling

Clinical Efficacy

• Alendronate reduces vertebral fractures by ~50%, multiple vertebral fractures by up to 90%, and hip fractures by up to 50% (Fracture Intervention Trial)
• Risedronate reduces vertebral fracture risk by 40-50% over 3 years and hip fracture risk by 40% in women with confirmed osteoporosis
• Ibandronate is primarily effective for vertebral fractures; hip fracture efficacy is less established
• Zoledronic acid (annual IV): equivalent efficacy, best for non-adherent patients or those with GI intolerance
• Harrison's Principles of Internal Medicine 22E, pp. 3347-3348

Administration - Critical Rules (Oral Agents)

1. Take on an empty stomach: Must be taken after an overnight fast; food (especially calcium-containing foods), coffee, tea, juice, and other medications significantly reduce absorption - Lippincott Illustrated Reviews: Pharmacology, p. 900
2. Take with a full glass (180-240 mL) of plain water only
3. Remain upright (sitting or standing) for at least 30 minutes after taking the tablet - to prevent the tablet from lodging in the esophagus and causing direct mucosal injury
4. Do not eat, drink (except water), or take other medications for at least 30 minutes after alendronate/risedronate (60 minutes for ibandronate)
5. Do not lie down for at least 30 minutes after administration

Adverse Effects

1. Gastrointestinal (Most Common - Oral Agents)

• Esophagitis and esophageal ulcers: The most clinically significant GI complication. Caused by direct chemical irritation of esophageal mucosa if the tablet is not cleared properly
• Oral bisphosphonates are contraindicated in patients with:
  • Esophageal stricture
  • Achalasia
  • Inability to stand/sit upright for ≥30 minutes
  • Severe dysphagia or inadequate esophageal emptying
• Upper GI symptoms: heartburn, dyspepsia, abdominal pain, nausea
• Note: In clinical trials, overall GI symptomatology was not significantly different from placebo, but in practice all oral bisphosphonates have been associated with esophageal irritation - Harrison's, p. 3347

2. Osteonecrosis of the Jaw (ONJ)

• Rare but serious; risk increases with longer duration of therapy
• Higher risk in patients receiving IV bisphosphonates for cancer-related indications
• Presents as exposed necrotic bone in the jaw, typically following dental procedures
• Prevention: complete any necessary dental work before starting bisphosphonate therapy

3. Atypical Femur Fractures (AFF)

• Rare, stress fractures of the subtrochanteric or diaphyseal femur
• Associated with prolonged bisphosphonate use (>5 years)
• May be bilateral; prodromal thigh/groin pain may precede fracture
• Mechanism: excessive suppression of bone turnover impairs normal micro-fracture repair

4. Acute-Phase Reaction (IV agents)

• Zoledronic acid first infusion can cause flu-like syndrome: fever, myalgia, arthralgia, headache
• Occurs in ~30% of patients with first dose; usually resolves within 72 hours
• Can be attenuated by pre-medication with acetaminophen

5. Hypocalcemia

• Especially with IV zoledronic acid; ensure calcium and vitamin D are adequate before infusion
• Lippincott Illustrated Reviews: Pharmacology, p. 900

6. Renal Toxicity

• IV bisphosphonates must be infused slowly (at least 15 minutes for zoledronic acid)
• Contraindicated if eGFR <35 mL/min

Drug Holiday

• Oral bisphosphonates: After 5 years of continuous therapy
• IV zoledronic acid: After 3 years

Comparison with Other Antiresorptives

• Goodman & Gilman's Pharmacological Basis of Therapeutics, p. 1084

Monitoring

• DXA scan every 1-3 years to assess BMD response
• Bone turnover markers (BTMs):
  • Serum CTX-I (resorption marker): maximally suppressed after ~8 weeks
  • PINP (formation marker): maximally suppressed after ~26 weeks
  • A >30% decrease in CTX-I is associated with greater fracture risk reduction
• Correct calcium and vitamin D deficiency before and during therapy - Rheumatology 2-Volume Set, p. 4372

Patient Education Summary (Administration Tips)

1. Take the tablet first thing in the morning, before any food, drink, or other medication
2. Swallow with a full glass of plain water (not juice, coffee, or milk)
3. Remain sitting or standing upright for at least 30 minutes - do not lie down
4. Do not eat or drink (except plain water) for 30 minutes (60 min for ibandronate)
5. Report any difficulty swallowing, chest pain, or heartburn immediately to your doctor
6. If you forget a weekly dose, take it the next morning - never take two doses on the same day