Zoledronic acid 5 mg intravenously once yearly is planned for a 71-year-old woman with osteoporosis. Which laboratory value is the absolute contraindication to administering this infusion?

• A Creatinine clearance of 28 mL/min ✓
• B Serum calcium of 8.0 mg/dL
• C Serum phosphate of 2.4 mg/dL
• D Serum 25-hydroxyvitamin D of 18 ng/mL

Explanation

Zoledronic acid is renally excreted and is not recommended when creatinine clearance falls below 35 mL/min because of the risk of worsening renal function. Hypocalcemia must be corrected before any bisphosphonate infusion, but a corrected calcium near normal with mild insufficiency values elsewhere is managed, not an absolute bar. Severe vitamin D deficiency should also be repleted first. B creatinine clearance of 28 mL/min therefore remains the deciding contraindication among these values.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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