Situation: A 62-year-old woman with breast cancer that has spread to her bones is admitted with confusion, constipation, thirst, and passing large amounts of urine. Her mucous membranes are dry. Her serum calcium is 13.6 mg/dL (3.39 mmol/L) (8.6–10.2 mg/dL; 2.15–2.55 mmol/L), and her albumin is 3.8 g/dL (38 g/L). After 24 hours of treatment, the physician orders zoledronic acid IV. Before starting it, the nurse reviews her results: Calcium: 12.4 mg/dL (3.09 mmol/L) (8.6–10.2 mg/dL) Potassium: 3.4 mEq/L (3.5–5.0 mEq/L) Serum creatinine: 1.9 mg/dL (168 µmol/L) (0.6–1.2 mg/dL) Magnesium: 1.8 mg/dL (1.7–2.2 mg/dL) What should the nurse do?

Zoledronic acid is cleared by the kidneys and can injure them, so kidney function is checked before each dose. Her creatinine of 1.9 mg/dL (168 µmol/L) is above normal, so the nurse reports it before starting; the physician may delay the dose, give more fluid first, or confirm that the benefit outweighs the risk. Her high calcium is the reason for the drug but does not override the kidney check, and a potassium of 3.4 mEq/L is not a reason to hold a bisphosphonate.

Core issue: Zoledronic acid is nephrotoxic, so renal function must be verified before each dose.

Zoledronic acid is a potent intravenous bisphosphonate used to treat hypercalcemia of malignancy and bone metastases. It is cleared primarily by the kidneys, and renal deterioration is recognized as the most significant toxicity associated with zoledronic acid ^[1]. Unlike oral bisphosphonates, which are not typically linked to meaningful nephrotoxicity, IV bisphosphonates carry a dose-dependent and infusion time-dependent risk of kidney injury ^[3]. Because of this, a serum creatinine level must be reviewed before each infusion is given.

In this patient, the serum creatinine is 1.9 mg/dL (168 µmol/L), which is above the reference range of 0.6–1.2 mg/dL. This is an important finding. The physician needs to know about this decline in renal function before the zoledronic acid is administered. Depending on the clinical picture, the physician may choose to delay the dose, provide additional IV hydration first, adjust the dose, or confirm that the expected benefit still outweighs the renal risk. The nurse should not independently start the infusion when creatinine is elevated without first reporting it.

Watch out! The calcium of 12.4 mg/dL (3.09 mmol/L) is still high, but that does not override the renal safety check. Hypercalcemia is the indication for the drug, not a reason to bypass the creatinine review. The potassium of 3.4 mEq/L is only mildly low and is not a contraindication to bisphosphonate therapy; it does not require correction before the infusion. The magnesium of 1.8 mg/dL is within normal limits.

Renal function monitoring is not a one-time step. Studies evaluating zoledronic acid in oncology patients have tracked serum creatinine at baseline, during treatment, and at peak levels because renal impairment can emerge over time ^[4]. In addition, zoledronic acid has been associated with both hypocalcemia and elevated serum creatinine in cancer patients, reinforcing the need to assess electrolytes and renal status together ^[2]. For this patient, the immediate priority is to report the elevated creatinine before starting the infusion.

Laboratory value	Result	Clinical relevance before zoledronic acid
Serum calcium	12.4 mg/dL	Still elevated; indicates ongoing need for treatment but does not bypass renal check
Serum creatinine	1.9 mg/dL	Elevated; must be reported because zoledronic acid is nephrotoxic and renally cleared
Potassium	3.4 mEq/L	Mildly low; not a reason to hold a bisphosphonate
Magnesium	1.8 mg/dL	Normal; no action needed

Key point! Before each zoledronic acid dose, verify serum creatinine and report any elevation above baseline or normal range. The drug’s nephrotoxicity is both dose-dependent and infusion time-dependent, so renal status directly influences whether the dose should be given, delayed, or modified ^[3].