A nurse is reviewing laboratory results for a client who has heart failure and notes a serum potassium level of 5.2 mEq/L (3.5 to 5.0 mEq/L). Which of the following medications should the nurse withhold?

Spironolactone is a potassium-sparing diuretic. In a client with hyperkalemia (K+ 5.2 mEq/L), administering spironolactone would further elevate potassium levels, risking life-threatening cardiac arrhythmias. The nurse should withhold this medication and notify the provider. Furosemide is a loop diuretic that actually lowers potassium — it may be appropriate here. Metoprolol (beta-blocker) and atorvastatin (statin) do not significantly affect potassium levels.