The effect of bisphosphonates on kidney function in osteoporotic geriatric patients with impaired renal function

Bisphosphonates are a mainstay treatment for osteoporosis, with prescribing guidelines based on creatinine clearance (CrCl). However, clinicians often use the estimated glomerular filtration rate (eGFR) from the CKD-EPI equation, which can lead to prescribing discrepancies in older adults, particularly in resource-limited settings where these agents are first-line therapy. To evaluate the real-world renal safety of bisphosphonates in older adults with discrepant renal function estimates (eGFR ≥ 35 mL/min/1.73 m² vs. CrCl < 35 mL/min) and assess renal function changes over 12 months. A retrospective cohort study was conducted in osteoporotic geriatric patients, all of whom had a baseline eGFR between 35 and 60 mL/min/1.73 m². These patients were then categorized into two groups based on their calculated CrCl: a CrCl < 35 mL/min group and a CrCl ≥ 35 mL/min group. Renal function was assessed at baseline, month 3, 6 and 12. The primary outcome was the change in renal function over time, analyzed using generalized estimating equations (GEE) with a group × time interaction term. A total of 222 patients (190 [85.6%] female; mean age 80.0 ± 6.5 years) were analyzed, with 109 (49.1%) in the CrCl < 35 group and 113 (50.9%) in the CrCl ≥ 35 group. Over the 12-month follow-up, the trajectories of renal function change—as measured by serum creatinine, eGFR, BSA-adjusted eGFR, and CrCl—did not significantly differ between the two groups (all p-values for interaction > 0.05). However, the CrCl < 35 group had a significantly higher adjusted relative risk (RR) of renal-related adverse events at 6 months (adjusted RR 6.77, 95% CI: 1.53 to 29.88) and 12 months (adjusted RR 3.75, 95% CI: 1.04 to 13.50). Calculating CrCl is essential before initiating bisphosphonate therapy in older adults. While long-term renal function trajectories were stable, the increased risk of acute adverse events in patients with CrCl < 35 mL/min underscores the need for careful monitoring. These findings suggest that bisphosphonates may be used cautiously in selected patients with impaired renal function, especially in resource-limited settings.