Renal Safety of Zoledronic Acid for Osteoporosis in Adults 75 years and Older

Introduction: Zoledronic acid (ZA) is used for the treatment of osteoporosis (OP). Renal impairment is a known risk factor for the rare occurrence of nephrotoxicity after ZA infusions, leading to use being contraindicated below creatinine clearance (CCr) of 35 mL/min. Our aims are to examine changes in serum creatinine (SCr) after infusions, capture frequency of acute kidney injury (AKI), and describe baseline kidney function estimates in adults 75 years and older being treated for OP.

Methods: This was a retrospective, cross-sectional, pre-post analysis that examined change in SCr before and after ZA infusions. The primary outcome was assessed using a paired Student t-test. Incidence of AKI within 1 year following infusions was noted and patient-specific factors were collected.

Results: Five hundred fifty-eight ZA infusions in 327 patients met criteria. Mean SCr decreased by 0.01 mg/dL in the year following ZA infusions (p = 0.005). AKI occurred in 1.4% of patients and all had CCr > 45 mL/min. 4.5% of patients had CCr < 35 mL/min and none experienced an AKI.

Conclusion: There was no clinically relevant change in SCr after ZA infusions. Risk of nephrotoxicity was low and similar to risk seen in randomized trials occurring in younger patients. Kidney function estimates were dramatically lower using the Cockcroft-Gault (CG) equation in comparison to CKD-EPI. We believe use of the CG equation in this population may be inappropriately limiting our ability to use ZA for treatment of OP in older adults but more evidence is necessary.