A nurse is reviewing the chart of a client who is scheduled to have radiological studies of the kidneys performed with the use of IV contrast dye. Which of the following client medications should the nurse withhold prior to the examination?

A. Pantoprazole: Pantoprazole is a proton pump inhibitor used to reduce gastric acid secretion. It does not interact with IV contrast dye and does not increase the risk of contrast-related complications, so it does not need to be withheld. B. Valsartan: Valsartan is an angiotensin II receptor blocker used to manage hypertension and heart failure. Although kidney function is monitored in clients taking this medication, it is not routinely withheld prior to contrast studies. C. Metformin: Metformin must be withheld before and for at least 48 hours after administration of IV contrast dye because contrast-induced nephropathy can lead to reduced renal clearance of metformin. This increases the risk of lactic acidosis, a serious and potentially fatal complication. D. Simvastatin: Simvastatin is a lipid-lowering medication and has no known interaction with IV contrast dye. It does not increase the risk of renal injury related to contrast administration and can be continued as prescribed.