07.2 Diuretics Flashcards
What is a diuretic?
A substance/drug that promotes a diuresis.
When would you use a diuretic?
In conditions where Na+ and water retention cause expansion of the ECF volume.
What is the mechanism of action of Loop diuretics, what substances are retained and which are lost?
NaK2Cl blockers
Loss of Na+, K+ and Ca2+
What are examples of loop diuretics?
Furosemide
Bumetanide
What is the mechanism of action of diuretics that act on the early distal tubule?
What substances are retained and which are lost?
Block NaCl transporter.
Na+ and K+ lost.
Ca2+ recovered.
What is an example of diuretics that act on the early distal tubule?
Bendroflumethiazide
What cells are targeted with diuretics that act on the late DCT and collecting duct?
Principle cells
What is the mechanism of action of diuretics that act on the principle cells of the late DCT and CD?
What substances are lost and which are retained?
Block ENaC.
Antagonise aldosterone.
Na+ lost.
K+ spared.
Where do carbonic anhydrase inhibitors act?
Brush border of the PCT where carbonic anhydrase is located.
When would carbonic anhydrase inhibitors be used?
Glaucoma.
What is mannitol?
A substance that is freely filtered but not absorbed.
Greatly increases the osmolarity of the filtrate which draws water into the urine.
What is mannitol used to treat?
Cerebral oedema.
Osmotic stress in plants.
Why give diuretics in nephrotic syndrome?
Low plasma albumin leads to oedema.
This leads to low circulatory level which leads to RAAS activation and more oedema occurs.
What specific conditions could you treat with diuretics?
Congestive heart failure.
Cirrhosis.
What is diuresis?
Increased formation of urine by the kidney
What two mechanisms cause loop and thiazide diuretics to cause the loss of potassium?
Increased water and sodium to DCT and CT.
1- higher flow rate means potassium is washed away quicker, this allows a concentration that is favourable for potassium secretion.
2- more sodium delivered means more reabsorption by principle cells, this creates a gradient favourable for potassium secretion.
What can you do when giving a potassium sparing diuretic to make sure the patient doesn’t become hyperkalaemic?
Give them a diuretic that causes the loss of potassium.
In someone with cirrhosis why would you give a potassium sparing diuretic over ones which causes potassium loss?
Hypokalaemia can precipitate hepatic encephalopathy - this can lead to a coma.
