07.2 Diuretics

Question 1

What is a diuretic?

Answer 1

A substance/drug that promotes a diuresis.

Question 2

When would you use a diuretic?

Answer 2

In conditions where Na+ and water retention cause expansion of the ECF volume.

Question 3

What is the mechanism of action of Loop diuretics, what substances are retained and which are lost?

Answer 3

NaK2Cl blockers

Loss of Na+, K+ and Ca2+

Question 4

What are examples of loop diuretics?

Answer 4

Furosemide

Bumetanide

Question 5

What is the mechanism of action of diuretics that act on the early distal tubule?
What substances are retained and which are lost?

Answer 5

Block NaCl transporter.
Na+ and K+ lost.
Ca2+ recovered.

Question 6

What is an example of diuretics that act on the early distal tubule?

Answer 6

Bendroflumethiazide

Question 7

What cells are targeted with diuretics that act on the late DCT and collecting duct?

Answer 7

Principle cells

Question 8

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?

Answer 8

Block ENaC.
Antagonise aldosterone.
Na+ lost.
K+ spared.

Question 9

Where do carbonic anhydrase inhibitors act?

Answer 9

Brush border of the PCT where carbonic anhydrase is located.

Question 10

When would carbonic anhydrase inhibitors be used?

Answer 10

Glaucoma.

Question 11

What is mannitol?

Answer 11

A substance that is freely filtered but not absorbed.

Greatly increases the osmolarity of the filtrate which draws water into the urine.

Question 12

What is mannitol used to treat?

Answer 12

Cerebral oedema.

Osmotic stress in plants.

Question 13

Why give diuretics in nephrotic syndrome?

Answer 13

Low plasma albumin leads to oedema.

This leads to low circulatory level which leads to RAAS activation and more oedema occurs.

Question 14

What specific conditions could you treat with diuretics?

Answer 14

Congestive heart failure.

Cirrhosis.

Question 15

What is diuresis?

Answer 15

Increased formation of urine by the kidney

Question 16

What two mechanisms cause loop and thiazide diuretics to cause the loss of potassium?

Answer 16

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.

Question 17

What can you do when giving a potassium sparing diuretic to make sure the patient doesn’t become hyperkalaemic?

Answer 17

Give them a diuretic that causes the loss of potassium.

Question 18

In someone with cirrhosis why would you give a potassium sparing diuretic over ones which causes potassium loss?

Answer 18

Hypokalaemia can precipitate hepatic encephalopathy - this can lead to a coma.