Diuretics and Renal Pharmacology Quiz

See Loop Diuretics. Option A is correct because loop diuretics such as furosemide and bumetanide block the Na-K-2Cl cotransporter (NKCC2) in the thick ascending limb of the loop of Henle. A cotransporter is a protein that carries several substances across the cell membrane together, here one sodium, one potassium and two chloride ions. The thick ascending limb normally reabsorbs about a quarter of all the sodium filtered by the kidney, so blocking it causes a large loss of sodium and water, and loop diuretics are the most powerful diuretics available. The BNF notes that loop diuretics inhibit reabsorption from the ascending limb of the loop of Henle and are powerful diuretics. The thick ascending limb is also where the kidney builds the concentration gradient in the medulla, so loop diuretics reduce the kidney's ability to concentrate urine. Clinically they are the workhorse drugs for heart failure and pulmonary oedema. An easy way to remember the site is that loop diuretics act on the loop, thiazides act on the distal tubule and the potassium-sparing drugs act at the collecting duct, the end of the line.

• Class: loop diuretics such as furosemide and bumetanide.
• Target: the Na-K-2Cl cotransporter (NKCC2) in the thick ascending limb of the loop of Henle.
• Effect: a large loss of sodium and water, making them the most powerful diuretics available.