Boonen S et al. (2008) Renal safety of annual zoledronic acid infusions in osteoporotic postmenopausal women. Kidney Int [doi:10.1038/ki.2008.193]

Intravenous administration of bisphosphonates such as zoledronic acid can reduce the risk of fractures in postmenopausal women with osteoporosis, but some studies have shown such treatment to be associated with deterioration in renal function. Boonen et al. recently reported renal safety results from HORIZON–PFT (Health Outcomes and Reduced Incidence with Zoledronic Acid Once Yearly—Pivotal Fracture Trial).

In total, 7,736 postmenopausal women with osteoporosis and creatinine clearance ≥30 ml/min who had not used intravenous bisphosphonates in the previous 2 years were randomly allocated to receive either placebo or 5 mg zoledronic acid as a 15 min intravenous infusion; two further infusions were given 12 months and 24 months later.

Serum creatinine levels 9–11 days after infusion increased by more than 44.2 µmol/l (0.5 mg/dl) from the preinfusion level in a higher percentage of zoledronic-acid-treated patients than placebo-treated patients (1.3% vs 0.4%; P = 0.001). However, serum creatinine levels returned to within 44.2 µmol/l (0.5 mg/dl) of the preinfusion level within 1 year in all zoledronic-acid-treated patients and in 80% of placebo-treated patients who had shown such increases. Over the 3 years of the study, mean changes in estimated creatinine clearance from baseline were similar in the two treatment groups, and there was no significant difference between groups in the percentages of patients experiencing a reduction in creatinine clearance, a creatinine clearance decrease of ≥30%, an increase in proteinuria or a renal adverse event.

The authors conclude that although annual zoledronic acid infusions can cause a transient reduction in renal function, long-term renal function is unaffected.