How do diuretics work?
All diuretics block sodium reabsorption by the kidney. Diuretics are classified according to the site in the nephron at which they block sodium reabsorption. There are four classes of diuretics.
• The thiazide diuretics (e.g., hydrochlorothiazide, chlorthalidone, and metolazone) inhibit the Na + -Cl − cotransporter in the luminal membrane of the distal tubule and connecting tubule.
• The loop diuretics (furosemide, bumetanide, torsemide, and ethacrynic acid) block the Na + -K + -2Cl − carrier in the luminal membrane of the thick ascending limb of the loop of Henle.
• The potassium-sparing diuretics (amiloride, triamterene, spironolactone, and eplerenone) block sodium reabsorption in the collecting tubule. Amiloride and triamterene inhibit Na + channels in the luminal membrane of the principal cell of the collecting tubule. Spironolactone and eplerenone are competitive inhibitors of aldosterone and indirectly block sodium reabsorption in the collecting tubule.
• The carbonic anhydrase inhibitor acetazolamide impairs proximal tubular Na + , Cl − , and HCO 3 − reabsorption.
