Osteoporosis Overview - Brittle Bones Battle
- Definition: Low bone mass & microarchitectural deterioration, leading to ↑ bone fragility. WHO diagnostic criterion: T-score ≤ -2.5.
- Major Risk Factors:
- Advanced age
- Postmenopausal status (↓ estrogen)
- Long-term corticosteroid use
- Smoking, excessive alcohol
- Goals of Therapy:
- Prevent fractures
- ↑ Bone Mineral Density (BMD)
- Reduce pain, maintain function
⭐ Most common osteoporotic fractures: vertebral, hip, and wrist.
Bisphosphonates - Mighty Mineral Binders
- MOA: Pyrophosphate analogs; bind hydroxyapatite in bone, inhibiting osteoclast activity and bone resorption.
- 📌 BPP: Bisphosphonates Prevent Pores.
- Key Agents:
- Oral: Alendronate, Risedronate, Ibandronate
- IV: Zoledronic acid, Pamidronate
- Oral Administration:
- Empty stomach (poor absorption).
- Full glass of plain water.
- Remain upright for 30-60 min (Alendronate/Risedronate 30 min; Ibandronate 60 min) to prevent esophagitis.
- Major ADRs:
- Esophagitis ⚠️ (oral)
- Osteonecrosis of the Jaw (ONJ)
- Atypical femoral fractures (long-term use)
- Hypocalcemia; Flu-like symptoms (IV)
- ⭐
Zoledronic acid is given once yearly IV for osteoporosis treatment.
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SERMs & Denosumab - Targeted Bone Defenders
| Feature | Raloxifene (SERM) | Denosumab |
|---|---|---|
| MOA | Estrogen agonist on bone; antagonist on breast & uterus | MAb vs RANKL; inhibits osteoclast formation & survival |
| Benefits | ↓ Vertebral fractures; ↓ invasive breast cancer risk | Broad ↓ fracture risk (vertebral, hip, non-vertebral) |
| Admin | Oral | SC q6 months |
| Key ADRs | Hot flashes, ↑ VTE risk (DVT/PE) | Hypocalcemia, skin issues, ONJ, atypical femoral fractures |
| 📌 Mnemonic | Raloxifene: Risk (VTE) vs Reward (bone/breast) | Denosumab: Deactivates osteoclasts via RANKL Directly |
Anabolic Agents & Calcitonin - Bone Growth Boosters
-
Anabolic Agents: Stimulate new bone formation.
- Teriparatide, Abaloparatide: Recombinant PTH analogues.
- MOA: Intermittent exposure stimulates osteoblasts > osteoclasts, ↑ bone mass.
- Use: Severe osteoporosis, patients at high fracture risk. Max 2 years therapy.
- ADRs: Hypercalcemia, orthostatic hypotension, leg cramps.
- ⚠️ BBW: Osteosarcoma risk (rats); avoid in Paget's disease, prior skeletal radiation.
⭐ Teriparatide treatment should be followed by an anti-resorptive agent to maintain BMD gains.
- Teriparatide, Abaloparatide: Recombinant PTH analogues.
-
Calcitonin (Salmon):
- MOA: Directly inhibits osteoclasts, ↓ bone resorption; provides analgesic effect.
- Forms: Nasal spray, injection.
- Use: Limited efficacy for osteoporosis; mainly for pain relief from acute vertebral compression fractures.
High‑Yield Points - ⚡ Biggest Takeaways
- Bisphosphonates (e.g., Alendronate) are first-line agents, inhibiting osteoclast activity; key risks include ONJ and atypical femoral fractures. Specific administration is crucial.
- Denosumab, an anti-RANKL monoclonal antibody, potently inhibits osteoclast function; administered as an SC injection every 6 months.
- Teriparatide (recombinant PTH) is an anabolic agent that stimulates osteoblast activity and bone formation; reserved for severe osteoporosis.
- Raloxifene, a SERM, inhibits bone resorption; it increases the risk of DVT/PE but decreases the risk of invasive breast cancer.
- Romosozumab, an anti-sclerostin antibody, has a dual effect: it increases bone formation and decreases bone resorption.
- Adequate Calcium and Vitamin D supplementation is essential alongside all pharmacological therapies for osteoporosis.
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