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.


Diuretics For Water Excretion

Image: “Water down the drain” by David Blackwell. License: CC BY 2.0


Overview of the Different Diuretics

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

Diuretics Active substances Renal target structure Effect on the serum electrolytes Drainage Effectiveness
Carbonic anhydrase inhibitors Acetazolamide, dorzolamide, brinzolamide Proximal tubule inhibition of the carbonic anhydrase Decreased sodium and bicarbonate, increased protons

Possibly hypokalaemia, hyperglycaemia

Not commonly used as a diuretic due to loss of electrolytes and bicarbonate
Loop diuretics Furosemide, bumetanide, piretanide, torasemide Thick ascending limb of the Henle loop, luminal Na-K-Cl-cotransporter, decreased reabsorption Decreased Na, K, Cl, Ca, Mg, decreased reabsorption of H2O in the collecting duct system (due to the changed osmotic gradient), possible hyperglycaemia, hyperuricaemia Most effective diuretic (20–30 % of the glomular filtrates)
Thiazide diuretics and thiazide analogues Hydrochlorothiazide, chlorthalidone, mefruside, xipamide Early distal inhibition of the Na-Cl-cotransporter, resulting in decreased NaCl reabsorption 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

Moderate effects (10–15 % of the glomular filtrates)
Potassium sparing diuretics Amiloride, Triamterene Late distal tubule and collecting duct system

Inhibition of sodium channels

Decreased Na, increased K Low effects (2–4 % of the glomular filtrates)
Aldosterone antagonists Spironolactone, potassium canrenoate, eplerenone Late distal tubule and collecting duct system

Competitive inhibition at the cytosolic mineralcorticoid receptor

Decreased Na, increased K Low effects (2–3 % of the glomular filtrates)
Osmotic diuretics Mannitol, sorbitol Unspecific effect in the whole tubule lumen osmodiuretically

Filtrated glomerularily and are not reabsorbed

Possible increased Na Low effects (2–3 % of the glomular filtrates)
Methylxanthines Theophylline, theobromine, caffeine Antagonist at the adenosine receptor (subtype A1), presumably inhibition of the basolateral Na-HCO3cotransporter in the proximal tubule Decreased Na and HCO3, increased H Little usefulness as diuretic due to adverse effects
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