High Ceiling Diuretics

Loop diuretics are the most powerful of all diuretics, they termed “high ceiling”.The loop diuretics drugs act primary on the thick segment of the ascending loop of Henle, inhibiting the transport of sodium chloride out of the tubule into the interstitial tissue by inhibiting the Na+ / K+ / 2Cl- carrier in the luminal membrane.

Loop diuretics abolish cortico medullary osmotic gradient and dicrease positive as well as negative free water clearance.

By inhibiting Na+ / K+ / 2Cl- symporter , absorbtion of Na+ in loop of henle decreases.This unabsorbed Na+ reaches DT , where it is exchanged with K+ and H+ resulting in hypokalemia and alkalosis. At equivalent doses loop diuretics cause less hypokalemia than Thiazides. These drugs also weakens CA inhibitors ( except ethacrynic acid, it does not increase bicarbonate excretion in the urine). Loop diuretics can also change intrarenal hemodynamics resulting dicreased absorbtion of Na+ and water in PT. These changes are mediated by the release of PGs. (NSAIDS attenuate diuretic effect) . Since GFR is not altered , loop diuretics are the diuretics of choice in moderate to severe renal failure.

  • Frusemide
  • Torsamide
  • Bumetanide
  • Ethacrynic acid
  • Piretanide
  • Axosemide
  • Tripamide
  1.  The loop diuretics have a venodilator action, directly and indirectly through the
    release of a renal factor.
  2. These drugs case potassium loss
  3. Loop diuretics produce a metabolic alkalosis

Clinical use of loop diuretics

1. In disease with salt and water over load due to:

  1. – acute pulmonary
  2. – chronic heart failure
  3. – hepatic cirrhosis with ascites
  4. – nephritic syndrome
  5. – renal failure

2. In hypertension
3. In acute treatment of hypercalcaemia as they cause excretion of Ca++.

Some points :

  • Furosemide has vasodialtory action and thus used in LVF and Pulmonary edema for quick action.
  • Bumetanide is the most potent loop diuretic with lesser side effects.
  • Ethacrynic acid is highly ototoxic with steep DRC.
  • Mersalyl has risk of kidney damage like oraganomercurials.
  • Torsemide has longest half life.

Adverse effects include hypokalemia, hypomagnesemia, alkalosis, hypergylcemia (C/I in DM), hyperuricemia (C/I in gout) and dyslipidemia (seen wit thiazides). Thiazides cause hypercalcemia while loop diuretics causes hypocalcemia.

Furosemides and bumetanide are sulfonamides in chemical nature and should be avoided in persons allergic to sulfonamides.



One Comment

  1. Konjengbam Ghanashyam says:

    Why are they called high ceiling?

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