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...