A 59-year-old man who is being treated for hypercholesterolemia, diabetes, and hypertension comes to the physician for a scheduled follow-up visit three weeks after starting a new medication. He has no new complaints. Blood work drawn yesterday shows an interim increase in potassium from 4.8 mEq/L to 5.2 mEq/L and a creatinine elevation from 1.2 mg/dL to 1.6 mg/dL. Administration of which of the following drugs is most likely responsible for the change in this patient's renal function?

Question

A 59-year-old man who is being treated for hypercholesterolemia, diabetes, and hypertension comes to the physician for a scheduled follow-up visit three weeks after starting a new medication.  He has no new complaints.  Blood work drawn yesterday shows an interim increase in potassium from 4.8 mEq/L to 5.2 mEq/L and a creatinine elevation from 1.2 mg/dL to 1.6 mg/dL.  Administration of which of the following drugs is most likely responsible for the change in this patient's renal function?

Quizplus · Accepted Answer

Angiotensin-converting enzyme (ACE) inhibitors (typically named "-pril") are one of the most important agents in treating hypertension, heart failure, and renal failure with or without proteinuria. They work by preventing the conversion of angiotensin I to angiotensin II. This prevents the efferent arteriole from constricting more than the afferent arteriole, thus decreasing the glomerular pressure and glomerular filtration rate (GFR). It is expected for the GFR to decrease in all patients initially. Most clinicians are generally not concerned by this unless the creatinine increases by greater than 30% because the long-term benefits of ACE inhibitors are well studied. Other common side-effects of ACE inhibitors include hyperkalemia and cough. (Choice B) Metoprolol is a beta-blocker. Typical side-effects include bradycardia and erectile dysfunction. Although beta blockers act upon the beta-1 receptors of the juxtaglomerular cells to reduce renin secretion, their use generally does not have a clinically significant effect on the GFR. (Choice C) Atorvastatin is an HMG-CoA reductase inhibitor; worrisome side-effects include muscle toxicity and hepatic dysfunction. Statins can uncommonly cause rhabdomyolysis, particularly when used in combination with fibrates or cyclosporin. However, massive rhabdomyolysis leading to acute kidney injury would most likely produce additional signs and symptoms such as myalgias, muscle weakness, dark urine, and elevated creatine kinase. (Choices D and E) Hydrochlorothiazide is a potassium-wasting thiazide diuretic that may decrease GFR if it results in volume depletion and pre-renal azotemia. Furosemide is also potassium-wasting loop diuretic. (Choice F) Metformin itself does not have nephrotoxic side effects. However, impaired renal function or recent IV contrast administration may reduce metformin excretion, resulting in systemic accumulation and possible lactic acidosis. (Choice G) Prazosin is an alpha-1 adrenergic antagonist that is used in the treatment of hypertension. It does not decrease the GFR. Educational objective: Common side-effects of ACE-inhibitors include decreased glomerular filtration rate (GFR), hyperkalemia, and cough. Angioedema is a rare, but life-threatening, side-effect.

A 59-Year-Old Man Who Is Being Treated for Hypercholesterolemia, Diabetes