Which drug is most likely to cause hyperkalemia when taken in excess?

Spironolactone is a potassium-sparing diuretic that works by acting as an antagonist to aldosterone in the distal nephron of the kidney. Aldosterone normally promotes the reabsorption of sodium and the excretion of potassium. By blocking this action, spironolactone decreases sodium reabsorption and reduces potassium excretion, which can lead to the retention of potassium in the bloodstream. When spironolactone is taken in excess, this effect is magnified, making hyperkalemia (an elevated level of potassium in the blood) a significant concern.

In contrast, furosemide is a loop diuretic that promotes the excretion of sodium, chloride, and potassium, decreasing the risk of hyperkalemia and more likely causing hypokalemia instead. Metoprolol, a beta-blocker, primarily affects cardiovascular function and does not have a direct effect on potassium levels. Amiodarone, an antiarrhythmic, can interact with many other medications and has a more complex profile, but is generally not associated with causing hyperkalemia when used within normal therapeutic ranges. Thus, spironolactone is uniquely positioned among these options as the drug most likely to contribute to hyperkalemia