Diuretics promote the generation of a negative fluid balance in the body. Additionally, nearly all diuretics increase the excretion of sodium in the kidneys, so that water is linked osmotically and also excreted. The different diuretics affect different parts of the tubule system.
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Overview of the Different Diuretics

The following gives an overview of the different renal target structures as well as the achieved effects associated with them.

Carbonic anhydrase inhibitors

Active substances: Acetazolamide, dorzolamide, brinzolamide

Renal target structure: Proximal tubule inhibition of the carbonic anhydrase

Effect on the serum electrolytes:

  • Decreased sodium and bicarbonate, increased protons
  • Possibly hypokalaemia, hyperglycemia

Drainage Effectiveness: Not commonly used as a diuretic due to loss of electrolytes and bicarbonate

Loop diuretics

Active substances: Furosemide, bumetanide, piretanide, torasemide

Renal target structure: Thick ascending limb of the Henle loop, luminal Na-K-Cl-cotransporter, decreased reabsorption

Effect on the serum electrolytes: Decreased Na, K, Cl, Ca, Mg, decreased reabsorption of H2O in the collecting duct system (due to the changed osmotic gradient), possible hyperglycaemia, hyperuricaemia

Drainage Effectiveness:

Most effective diuretic (20–30 % of the glomular filtrates)

Thiazide diuretics and thiazide analogues

Active substances: Hydrochlorothiazide, chlorthalidone, mefruside, xipamide

Renal target structure: Early disinhibition of the Na-Cl-cotransporter, resulting in decreased NaCl reabsorption

Effect on the serum electrolytes:

  • Decreased Na, Cl, Mg, decreased K (as a lot of Na can be exchanged for K in the late distal tubule)
  • Increased Ca
  • Possibly hyperglycaemia, hyperuricaemia

Drainage Effectiveness: Moderate effects (10–15 % of the glomular filtrates)

Potassium sparing diuretics

Active substances: Amiloride, Triamterene

Renal target structure: 

  • Late distal tubule and collecting duct system
  • Inhibition of sodium channels

Effect on the serum electrolytes: Decreased Na, increased K

Drainage Effectiveness: Low effects (2–4% of the glomular filtrates)

Aldosterone antagonists

Active substances: Spironolactone, potassium canrenoate, eplerenone

Renal target structure:

  • Late distal tubule and collecting duct system
  • Competitive inhibition at the cytosolic mineralcorticoid receptor

Effect on the serum electrolytes: Decreased Na, increased K

Drainage Effectiveness: Low effects (2–3 % of the glomular filtrates)

Osmotic diuretics

Active substances: Mannitol, sorbitol

Renal target structure:

  • Unspecific effect in the whole tubule lumen osmodiuretically
  • Filtrated glomerularily and are not reabsorbed

Effect on the serum electrolytes: Possible increased Na

Drainage Effectiveness: Low effects (2–3 % of the glomular filtrates)

Methylxanthines

Active substances: Theophylline, theobromine, caffeine

Renal target structure: Antagonist at the adenosine receptor (subtype A1), presumably inhibition of the basolateral Na-HCO3cotransporter in the proximal tubule

Effect on the serum electrolytes: Decreased Na and HCO3, increased H

Drainage Effectiveness: Little usefulness as diuretic due to adverse effects

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