When caring for a patient on multiple cardiac medications, the nurse notices signs of hypokalemia. Which medication is most likely contributing?

Choice A rationale Furosemide is a loop diuretic that inhibits the reabsorption of sodium and chloride in the thick ascending limb of the loop of Henle. This action increases the excretion of these ions, as well as potassium, through the kidneys. The increased urinary potassium loss can lead to hypokalemia, a common and potentially dangerous side effect requiring careful monitoring of serum potassium levels (normal range 3.5-5.0 mEq/L). Choice B rationale Spironolactone is a potassium-sparing diuretic that acts as a competitive antagonist of aldosterone in the distal convoluted tubule and collecting duct. By blocking aldosterone's effects, it promotes the excretion of sodium and water while promoting the reabsorption of potassium. This mechanism increases serum potassium levels, and therefore, this medication is more likely to cause hyperkalemia, not hypokalemia. Choice C rationale Lisinopril is an ACE inhibitor (angiotensin-converting enzyme inhibitor). It blocks the conversion of angiotensin I to angiotensin II, leading to decreased aldosterone secretion. Decreased aldosterone reduces the retention of sodium and water and the excretion of potassium. Therefore, lisinopril is more likely to cause hyperkalemia rather than hypokalemia, making it an unlikely cause. Choice D rationale Metoprolol is a beta-blocker that works by blocking the effects of catecholamines on beta-adrenergic receptors. It primarily affects the heart by slowing the heart rate and reducing contractility, thereby lowering blood pressure. It does not directly impact the renal tubules or the handling of potassium, so it is not a direct cause of hypokalemia. Its effect on potassium is considered negligible.