Spironolactone is a potassium-preserving diuretic, and furosemide is a potassium-removing diuretic. The combination of the two drugs can treat edematous disorders by excreting excess sodium and water in the body to reduce the volume of extracellular fluid and eliminate edema. It can treat edema due to congestive heart failure, cirrhotic ascites, nephrotic syndrome, acute or chronic nephritis, early stages of chronic renal insufficiency or sodium and water retention due to adrenocorticotropic hormone syndrome. Patients with hypertension may also be treated with a combination of both, or with other antihypertensive drugs. However, it is important to monitor the blood potassium closely when combining the two drugs, as it can lead to water-electrolyte disturbances, especially hypokalemia. If severe hypokalemia occurs, side effects and complications such as cardiac arrhythmias can occur, so special attention should be paid to potassium supplementation.