Before administering an antibiotic that can cause nephrotoxicity, which laboratory value is most important for the practical nurse (PN) to review?

Serum creatinine is the most important laboratory value to review before administering an antibiotic that can cause nephrotoxicity. Nephrotoxicity is an alteration in the function of the kidney due to exposure to certain drugs or toxins. It can be assessed by measuring the glomerular filtration rate (GFR), which is the rate of clearance of a substance from the blood by the kidneys. Serum creatinine is a waste product of muscle metabolism that is freely filtered by the glomeruli and not reabsorbed or secreted by the tubules. Therefore, it is a reliable indicator of GFR and renal function. An increase in serum creatinine indicates a decrease in GFR and renal function, which may be caused by nephrotoxic drugs. The other laboratory values are not directly related to nephrotoxicity or GFR: Serum calcium: This may be affected by renal function, but it is not a sensitive or specific marker of nephrotoxicity. It may be altered by other factors such as vitamin D, parathyroid hormone, and bone metabolism. Hemoglobin and hematocrit: These may be affected by renal function, but they are not sensitive or specific markers of nephrotoxicity. They may reflect the erythropoietin production by the kidneys, which stimulates red blood cell production in the bone marrow. However, they may also be influenced by other factors such as blood loss, hydration status, and iron deficiency. White blood cell count (WBC): This is not related to nephrotoxicity or GFR. It may reflect the presence of infection or inflammation, which may be a cause or a consequence of renal impairment, but it is not a direct measure of renal function.