Types

Carbonic Anhydrase Inhibitor

• Acts on proximal convoluted tubule
• Inhibits the enzyme carbonic anhydrase, which is normally involved in the breakdown of carbonic acid into carbon dioxide and water
  • Inhibition of carbonic anhydrase leads to a build-up of bicarbonate instead, as the alternate pathway for carbonic acid metabolism
  • Because there is now too much of it, more bicarbonate is set free into the urine
  • But hydrogen ions are used as currency to exchange for the resorption of sodium ions, so a diuretic effect ensues
• Examples: acetazolamide
  • The name has “c” and “a” in it

Loop

• Acts on thick ascending limb of Loop Of Henle
• Blocks Na+-K+-2Cl- transporter
  • This has four ions in it, just as “loop” has four letters in it, as does the word “four“
• Examples: frusemide/furosemide

Thiazide

• Acts on distal convoluted tubule
• Blocks Na+-Cl- channel, affectionately called NKCC pump
  • This has two ions in it and “thiazide” starts with “t” too
• Examples: hydrochlorothiazide

Potassium-Sparing

• Acts on collecting duct
• Does not evict potassium into urine for an ungracious hypokalaemia like the others
• Examples: amiloride, spironolactone
  • Amiloride
    • Blocks epithelial Na+ channel, affectionately called ENaC
  • Spironolactone
    • Aldosterone antagonist

Others

Diuresis refers to the increased production of urine. Thus, further substances exist that can exact a diuretic effect but do not work on kidneys in the ways listed above. For example, coffee can have a weak diuretic effect, while that of alcohol is stronger.

Diuretic Actions On Calcium

Loop –> Hypocalcaemia

Thiazide –> Hypercalcaemia

Triple Whammy

• Diuretic
• ACE inhibitor or ARB
• NSAID

References

1. Chaudhry, S. (2017). DIURETICS AND RENAL HORMONES. [online] McMaster Pathophysiology Review. Available at: http://www.pathophys.org/diuretics/ [Accessed 12 Sep. 2017].