Diuretics

Question 1

What do diuretics do?

Answer 1

• Act on kidneys to increase urine production and eliminate water from the body
• Reduce plasma volume and cardiac output
• Reduce BP
• Reduce oedema/ascites

Question 2

What are diuretics?

Answer 2

• Drugs that increase renal excretion of Na+ and water
• Result in an increase in urine volume

Question 3

What is diuresis?

Answer 3

• The process of excretion of water in the urine

Question 4

What is natriuresis?

Answer 4

• The process of excretion of sodium in the urine

Question 5

What are the 5 main classes of diuretics?

Answer 5

• Carbonic anhydrase inhibitors
• Osmotic diuretics
• Loop diuretics
• Potassium sparing diuretics
• Thiazide and thiazide-like diuretics

Question 6

Which structures do diuretics affect?

Answer 6

• Carriers or transporters in the luminal membrane or renal tubular cells

Question 7

Which classes of diuretic act on the PCT?

Answer 7

• Carbonic anhydrase inhibitors
• Osmotic diuretics

Question 8

Which class of diuretic acts on the loop of Henle?

Answer 8

• Loop diuretics

Question 9

Which classes of diuretic act on the DCT?

Answer 9

• Thiazide and thiazide-like diuretics
• Potassium sparing diuretics (late DCT and early CD)

Question 10

How do loop diuretics cause hypokalaemia?

Answer 10

• ENac channels work harder to move Na+ out of collecting duct and into cells
• K+ then leaves these cells via ROMK channels because the extra Na+ makes the positive charge in the cells too high
• K+ is then excreted
• This can cause hypokalaemia

Question 11

Give an example of an osmotic diuretic?

Answer 11

• Mannitol - administered via IV

Question 12

What is the action of osmotic diuretics?

Answer 12

• Allow water diuresis without affecting Na+ excretion
• Expands extracellular fluid volume initially
• Decreases blood viscosity
• Inhibits renin release
• Increases renal blood flow

Question 13

What are the uses of osmotic diuretics?

Answer 13

• Treat acute renal failure due to shock or trauma (maintains urine flow and preserves kidney function)
• Treat acute drug poisoning by eliminating drugs before they are absorbed from renal tubules
• Decreases intracranial and intraocular pressure before ophthalmic or brain procedures

Question 14

Why don’t we use osmotic diuretics often?

Answer 14

• Can expand extra-cellular volume
• Water stays in plasma as it travels to kidney
• Could cause problems in certain patients e.g. with heart failure

Question 15

What are the side effects of osmotic diuretics?

Answer 15

• Headache, nausea, vomiting due to hyponatraemia
• Extracellular volume expansion - complicates heart failure and pulmonary oedema
• Contraindicated in chronic heart failure
• Excessive use needs to dehydration and hypernatraemia

Question 16

What is the action of loop diuretics?

Answer 16

• Inhibit Na+/K+/2Cl- transporter

Question 17

Give examples of loop diuretics

Answer 17

• Bumetanide
• Furosemide

Question 18

How are loop diuretics administered?

Answer 18

• Orally or via IV
• Have a fast onset of action
• Increase urine volume
• Suitable for emergency situations

Question 19

What do we use loop diuretics to treat?

Answer 19

• Severe oedema associated with congestive heart failure
• Treatment for Oliguric ARF
• Treatment of hypercalcaemia
• Acute pulmonary oedema
• Acute hyperkalaemia
• Acute hypercalcaemia
• Toxicity of Br, F and I

Question 20

What are the side effects of loop diuretics?

Answer 20

• Hypovolaemia
• Hyponatraemia
• Hypokalaemia - dietary supplementation or K-sparing diuretics should be used
• Hypomagnesaemia
• Metabolic alkalosis
• Postural hypotension

Question 21

What is the action of thiazide and thiazide like diuretics?

Answer 21

• Inhibit Na+/Cl- transporter
• 1st line antihypertensive

Question 22

What are the effects of thiazide and thiazide like diuretics?

Answer 22

• Increase urinary NaCl excretion
• Increase urinary K+ excretion
• Increase urinary Mg2+ excretion
• Increase Ca2+ reabsorption
• Decrease urinary Ca2+ excretion
• Decrease uric acid excretion

Question 23

Give some examples of thiazide and thiazide-like diuretics

Answer 23

• Bendroflumethiazide
• Indapamide

Question 24

What are thiazide and thiazide-like diuretics used to treat?

Answer 24

• Essential hypertension
• Mild heart failure
• Calcium nephrolithiasis due to hypercalciuria
• Osteoporosis
• Nephrogenic diabetes insipidus polyuria

Question 25

What is the action of potassium sparing diuretics?

Answer 25

- Blocks ENac channel - No change in electrochemical gradient (because no movement of Na+)so no K+ is lost

Question 25

What is the action of potassium sparing diuretics?

Answer 25

- Blocks ENac channel - No change in electrochemical gradient (because no movement of Na+) so no K+ is lost

Question 26

What is the action of aldosterone antagonists?

Answer 26

- Acts as a competitor for the aldosterone receptors - No increase in ENac channels or ROMK channels - No loss of K+ or Na+

Question 27

Give an example of a potassium sparing diuretic?

Answer 27

- Amiloride

Question 28

Give an example of an aldosterone antagonist

Answer 28

- Spironolactone

Question 29

What are the effects of potassium sparing diuretics and aldosterone antagonists?

Answer 29

- Increase urinary Na+ excretion - Decrease urinary K+ excretion - Decrease H+ excretion

Question 30

What are the uses of potassium sparing diuretics and aldosterone antagonists?

Answer 30

- Secondary hyperaldosteronism - CHF, hepatic cirrhosis, nephrotic syndrome - Treatment of hypertension (combined with thiazide or loop diuretics)

Question 31

Which patients are potassium sparing diuretics and aldosterone antagonists contraindicated in?

Answer 31

- Hyperkalaemia (chronic renal failure, k+ supplementation, beta-blockers, ACE inhibitors) - Liver disease