Zoledronic Acid

Chemical Identity

Property	Value
Chemical Formula	C5H10N2O7P2
Molecular Weight	272.1 Da
CAS Number	118072-93-8
Peptide Class	Bisphosphonate (Non-peptide Mimetic)
Route	IV, oral

Structure

Zoledronic acid (Zometa, Reclast) is a third-generation nitrogen-containing bisphosphonate with an imidazole ring. While not a peptide, bisphosphonates mimic pyrophosphate and interact with bone mineral hydroxyapatite. The nitrogen-containing side chain determines its potency and mechanism.

Mechanism of Action

Zoledronic acid binds to hydroxyapatite in bone, concentrating at sites of active remodeling. Internalized by osteoclasts, it inhibits farnesyl pyrophosphate synthase (FPPS) in the mevalonate pathway, preventing protein prenylation of small GTPases essential for osteoclast function, survival, and ruffled border formation.

Clinical Applications

• Osteoporosis: Annual 5 mg IV infusion (Reclast)
• Bone metastases: Monthly 4 mg for skeletal-related events (Zometa)
• Multiple myeloma: Bone disease management
• Paget’s disease: Single 5 mg infusion
• Hypercalcemia of malignancy: Standard treatment

Pharmacokinetics

• Half-life: 146 hours (terminal, bound to bone)
• Protein binding: 22% (plasma), >90% (bone)
• Elimination: Renal (unchanged)
• Bone retention: Years
• Route: IV infusion over 15 minutes

Safety and Side Effects

Flu-like symptoms (acute phase reaction), osteonecrosis of the jaw (ONJ), atypical femoral fractures (rare), hypocalcemia, nephrotoxicity, and uveitis. Renal monitoring required.

References

• Major, P., et al. (2001). Zoledronic acid for bone metastases. New England Journal of Medicine, 345, 1098-1106.
• Black, D.M., et al. (2007). HORIZON trial: zoledronic acid for osteoporosis. New England Journal of Medicine, 356, 1809-1822.