Bisphosphonates are a class of drugs that inhibit bone resorption by osteoclasts, used in oncology for prevention and treatment of skeletal complications in cancers with bone involvement, and in supportive care for osteoporosis secondary to cancer treatment.
Pharmacological Class
- Anti-resorptive agents
- Analogues of pyrophosphate, with strong affinity for bone mineral (hydroxyapatite)
Mechanism of Action
- Bind to bone mineral, especially at sites of active resorption.
- Nitrogen-containing bisphosphonates (e.g., zoledronic acid, pamidronate) inhibit farnesyl pyrophosphate synthase in the mevalonate pathway → osteoclast apoptosis.
- Non-nitrogen bisphosphonates (e.g., clodronate, etidronate) get incorporated into toxic ATP analogs in osteoclasts → apoptosis.
- Result: ↓ bone turnover, ↓ skeletal-related events (SREs).
Oncology Indications
- Bone metastases from solid tumors (e.g., breast, prostate, lung)
- Multiple myeloma with lytic bone lesions
- Hypercalcemia of malignancy
- Osteoporosis prevention in patients on long-term corticosteroids or aromatase inhibitors
Common Agents in Oncology
| Generic | Brand | Usual Dose in Oncology | Route |
|---|---|---|---|
| Zoledronic acid | Zometa® | 4 mg IV over ≥15 min every 3–4 weeks | IV |
| Pamidronate | Aredia® | 90 mg IV over 2–4 hours every 3–4 weeks | IV |
| Clodronate | Bonefos® | 1,600 mg PO daily | PO |
| Ibandronate | Bondronat® | 6 mg IV every 3–4 weeks or 50 mg PO daily | IV/PO |
Key Clinical Benefits
- Reduce risk of pathologic fractures
- Reduce spinal cord compression risk
- Reduce need for radiotherapy or surgery to bone
- Control bone pain
- Manage hypercalcemia of malignancy
Adverse Effects
- Acute phase reaction (fever, myalgia, flu-like symptoms after first infusion)
- Hypocalcemia, hypophosphatemia
- Renal toxicity (more with zoledronic acid—adjust dose in renal impairment)
- Osteonecrosis of the jaw (ONJ) — risk increased with invasive dental work, poor oral hygiene
- Atypical femur fractures (rare, with long-term use)
- GI irritation (oral forms)
Oncology Pharmacist Considerations
- Baseline dental evaluation before starting; avoid invasive dental procedures during therapy when possible.
- Correct hypocalcemia & vitamin D deficiency before initiation.
- Monitor serum creatinine prior to each dose; adjust dosing for CrCl <60 mL/min.
- Counsel patients on good oral hygiene and prompt reporting of jaw pain or loose teeth.
- In hypercalcemia of malignancy, ensure aggressive IV hydration prior to bisphosphonate infusion.
Synonyms
Alendronate, Risedronate, Etidronate