Drugs for Osteoporosis

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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 Healthy vs Osteoporotic Bone Microstructure

⭐ 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.

Bisphosphonate mechanism of action on boneoka

SERMs & Denosumab - Targeted Bone Defenders

RANK-RANKL pathway and Denosumab mechanism of action

FeatureRaloxifene (SERM)Denosumab
MOAEstrogen agonist on bone; antagonist on breast & uterusMAb vs RANKL; inhibits osteoclast formation & survival
Benefits↓ Vertebral fractures; ↓ invasive breast cancer riskBroad ↓ fracture risk (vertebral, hip, non-vertebral)
AdminOralSC q6 months
Key ADRsHot flashes, ↑ VTE risk (DVT/PE)Hypocalcemia, skin issues, ONJ, atypical femoral fractures
📌 MnemonicRaloxifene: 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.

  • 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.

PTH effects on bone cells and osteoblast differentiation

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.

Practice Questions: Drugs for Osteoporosis

Test your understanding with these related questions

A 60-year-old elderly female with a previous history of a Colles fracture is now complaining of backache. Which of the following statements regarding the treatment of this patient is incorrect?

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Flashcards: Drugs for Osteoporosis

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_____ is contraindicated in patients with prior history of radiation, for treatment of osteoporosis.

TAP TO REVEAL ANSWER

_____ is contraindicated in patients with prior history of radiation, for treatment of osteoporosis.

Teriparatide

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