Wednesday, 10 November 2010

MRCP revision battle 45.3: Diuretics

Before I started my revision I thought I was very au-fait with diuretics - after all, I prescribe them daily.  However, a quick bond with the British National Formulary revealed some interesting gems.  So here's a quick recap of diuretics with a sprinkling of hopefully new information.

1. Loop diuretics
  • work on the Na-K-2Cl transporter in the ascending loop of Henle
  • examples include furosemide and bumetanide
  • bumetanide is 40x more potent than furosemide for the same dose
  • both work within 30 mins (if given IV) or 1 hr (if given orally) and their action is completed within 6 hours
  • possible side effects include:
    • hypokalaemia/natraemia
    • retention if enlarged prostate
    • tinnitus 
    • pancreatitis

2. Thiazide diuretics
  • work on the Na-Cl co-transporter in the DCT
  • examples include bendroflumethiazide, indapamide and metolazone
  • they work within 1 to 2 hours and have a duration of action of 12 to 24 hours
  • possible side effects include:
    • hypokalaemia/naturaemia
    • hyperglycaemia
    • pancreatitis

3. Aldosterone antagonists
  • work by antagonising aldosterone 
  • examples include spironolactone and eplerenone 
  • possible side effects include:
    • hyperkalaemia
    • impotenence
    • gynaecomastia

Now for the differentials of proteinuria...