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


  • 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


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


  • Acts on collecting duct
  • Does not evict potassium into urine for an ungracious hypokalaemia like the others
  • Examples: amiloride, spironolactone


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


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

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