Diuretics

Question 1

What are diuretics?

Answer 1

Diuretics are a common medication that work to diminish sodium reabsorption at different sites of the nephron in order to increase urinary sodium and water loss.

Question 2

What is acetazolamide?

Answer 2

A carbonic anhydrase inhibitor (form of diuretic)

Question 3

What is the main use of carbonic anhydrase inhibitors such as acetazolamide?

Answer 3

The main use of these drugs is not as a diuretic, but is used in the treatment of glaucoma, epilepsy and mountain sickness (as it can induce a metabolic acidosis to compensate for the respiratory alkalosis that occurs with hyperventilation at altitude)

Question 4

Explain how carbonic anhydrase inhibitors (such as acetazolamide) act as diuretics

Answer 4

You stop reabsorbing sodium, and you stop excreting hydrogen ions which means that more water leaves the blood due to the increased levels of sodium in the renal tubule

Question 5

What are the side-effects of carbonic anhydrase inhibitors such as acetazolamide?

Answer 5

Metabolic acidosis can occur (contra-indicated in significant chronic kidney disease), sedation and can lead to bone marrow suppression (due to action as a sulphonamide antibiotic)

Question 6

What is the most potent type of diuretic?

Answer 6

Loop diuretic

Question 7

What are frusemide and bumetanide?

Answer 7

Loop diuretics

Question 8

What are loop diuretics used to treat?

Answer 8

This is the most potent diuretic and it is used in the treatment of hypertension, heart failure and volume overload fom chronic renal failure

Question 9

Explain the mechanism of action of loop diuretics

Answer 9

Blockage of the Na+/K+/Cl- transporter leads to the dysfunction of the entire loop mechanism as these aren’t pumped out of the tubule into the interstitium in the thick ascending limb, and therefore water and electrolytes won’t diffuse down the concentration gradient at the thin descending limb, and therefore the urine will remain dilute a nd there will be loss of sodium, magnesium, sodium and calcium

Question 10

Name two loop diuretics

Answer 10

Frusemide and bumetanide

Question 11

What are the side-effects of loop diuretics?

Answer 11

hypokalaemia, dehydration (which can lead to acute renal failure), kidney stones and deafness

Question 12

What are Bendroflumethiazide and Hydrochlorothiazide?

Answer 12

Thiazide diuretics

Question 13

Name some thiazide diuretics

Answer 13

Bendroflumethiazide, Hydrochlorothiazide and Thiazide-like drugs such as Chlorthalidone, Indapamide and Metolazone

Question 14

Why may an individual be prescribed thiazide diuretics?

Answer 14

Primarily used as an anti-hypertensive but can also work to reduce plasma volume and peripheral resistance

Question 15

What is the mechanism of action of thiazide diuretics?

Answer 15

Inhibits the Na+/Cl- symporter in the distal convoluted tubule, therefore these molecules remain in the tubular fluid and cause the formation of more dilute urine

Question 16

What are the side-effects of thiazide diuretics?

Answer 16

Hypokalaemia, hypercalcaemia, hyponatraemia, hyperglycaemia and hypercholesterolaemia

Question 17

Which kinds of diuretics are ‘potassium-sparing’?

Answer 17

Epithelial sodium channel antagonists (amiloride and triamterene) and aldosterone antagonists (spironolactone and epleronone)

Question 18

What are amiloride and triamterene?

Answer 18

These are epithelial sodium channel antagonists, and are therefore potassium-sparing diuretics

Question 19

What are spironolactone and eplerenone?

Answer 19

Aldosterone antagonists which are a form of potassium-sparing diuretic

Question 20

Why may an individual be prescribed amiloride (an epithelial sodium channel antagonist)?

Answer 20

Amiloride this is used in the treatment of heart failure, hypokalamia (produced by other diuretics) and liver cirrhosis

Question 21

Explain the mechanism of action of amiloride (epithelial sodium channel antagonist)

Answer 21

It blocks the sodium channel on the principal cells of the collecting tubule and therefore prevents the diffusion of sodium into the cells and into the blood where there would be an osmotic gradient for water reabsorption.

Question 22

What side-effects may occur as a result of taking amiloride or triamterene (epithelial sodium channel antagonists)?

Answer 22

Hyperkalaemia (it’s a potassium-sparing diuretic) and hyponatraemia

Question 23

Why may an individual be prescribed spironolactone or eplerenone (aldosterone antagonist)?

Answer 23

Used in hyperaldosteronism, heart failure, hypokalaemia (from other diuretics) and cirrhosis

Question 24

Explain the mechanism of action of spironolactone or eplerenone (aldosterone antagonist)

Answer 24

Antagonist of aldosterone, acting primarily through competitive binding of receptors at the aldosterone-dependent sodium-potassium exchange site; this causes increased potassium uptake but increased sodium and water excretion –> increased water loss.

Question 25

What side effects may occur as a result of taking spironolactone or eplernone (aldosterone antagonist)?

Answer 25

HYPERKALAEMIA! Gynaecomastia (not with epleronone) and hyponatraemia

Question 26

Name two types of osmotic diuretic?

Answer 26

Mannitol and glucose

Question 27

Why may an individual be prescribed an osmotic diuretic?

Answer 27

If they have cerebral oedema and oliguric (reduced urinary output) acute renal failure

Question 28

How do osmotic diuretics work?

Answer 28

These are osmotically active molecules that are freely filtered in the glomerulus and not reabsorbed by the tubules water follows this osmotic gradient into the tubule fluid and also decreased the reabsorption of all solutes in general such as sodium, potassium, urea and ‘drags’ sodium from the interstitial space

Question 29

What are the potential consequences of using osmotic diuretics?

Answer 29

Can cause transient fluid overload which can lead to pulmonary oedema

Question 30

When shouldn’t you use diuretics?

Answer 30

If an individual is hypotensive, dehydrated, hypokalaemia (no thiazide or loop diuretics) or hyperkalaemic (no spironolactone or amlidoride), or post-surgery if there’s a low urinary output.

Question 31

On which cells do thiazide diuretics act?

Answer 31

Distal convoluted tubule

Question 32

On which cells do loop diuretics act?

Answer 32

Thick ascending limb of Loop of Henle

Question 33

On which cells do carbonic anhydrase inhibitors act?

Answer 33

Proximal convoluted tubule

Question 34

Where do potassium sparing diuretics act?

Answer 34

Collecting tubule