A 54-year-old obese man was diagnosed with NIDDM 1 year earlier. He was started on glipizide and metformin. His other medications are propranolol and nifedipine for hypertension, and naproxen, which he began 2 weeks ago for severe osteoarthritis. His BP is 154/92. His BUN is 29 mg/dL and a creatinine of 1.8 mg/dL; both had been normal 1 year earlier. Which medications is most likely responsible for the increase in BUN and creatinine?

The use of nonsteroidal anti-inflammatory drugs (NSAIDs), such as naproxen, may cause a usually mild renal insufficiency, possibly related to a mild interstitial nephritis or glomerulonephritis. Risk of NSAID-induced renal damage is increased in the elderly and in patients with underlying renal disease. Glipizide a second-generation sulfonylurea, may predispose patients to hypoglycemia but is not associated with renal toxicity. Metformin does not induce renal damage but should be used cautiously in patients with underlying renal damage because of the possibility of developing lactic acidosis.  Neither nifedipine nor propranolol has a tendency to adversely affect the kidneys.