Spironolactone is a long acting potassium diuretic and furosemide is a short-acting loop diuretic. Spironolactone and Furosemide have different but complementary mechanisms and site of action. Therefore, when given together they produce synergistic or additive diuretic effects. Spironolactone is a competitive inhibitor of the binding of aldosterone to its receptors. Its most important site of action is the distal portion of renal tubules. Spironolactone acts both as a diuretic and antihypertensive drug by antagonizing the sodium retaining effects of aldosterone. Furosemide is a potent diuretic acting primarily on the medullary portion of the ascending limb of the Loop of Henle to inhibit a Na+/K+/2Cl- co-transporter which normally mediates ionic reabsorption. Furosemide inhibits sodium and potassium reabsorption by competing for the luminal face of epithelial cells and thereby removes the stimulus of water reabsorption. It also inhibits sodium reabsorption in other nephron segment.