11. Diuretics

Question 1

What is the general role of diuretics?

Answer 1

Act on kidney to increase production of urine and to eliminate water from the body

Question 2

What can diuretics help to do?

Answer 2

Reduce plasma volume and cardiac output
Reduce blood pressure
Reduce oedema/ascites

Question 3

What are the 5 main classes of diuretics?

Answer 3

Carbonic anhydrase inhibitors
Osmotic diuretics
Loop diuretics
Potassium sparing diuretics
Thiazides and thiazides-like diuretics

Question 4

Generally, how do diuretics work?

Answer 4

Act by interfering with the normal sodium reabsorption by the renal tubules resulting in Na+ and water excretion

Question 5

Where in the nephron do carbonic anhydrase inhibitors and osmotic diuretics act?

Answer 5

PCT

Question 6

Where in the nephron do loop diuretics act?

Answer 6

Thick ascending limb of loop of Henle

Question 7

Where do thiazide and thiazides like diuretics act in the nephron?

Answer 7

DCT

Question 8

Where do potassium sparing diuretics act in the nephron?

Answer 8

Late DCT and CD

Question 9

How do carbonic anhydrase inhibitors work?

Answer 9

Inhibit carbonic anhydrase, less H2O and CO2 are taken up into the cell, therefore less Na+ is reabsorbed from the cells in proximal tubule

Question 10

Give an example of an osmotic diuretic

Answer 10

Mannitol (IV)

Question 11

How do osmotic diuretics work?

Answer 11

Mannitol in blood, moves into tubule at kidney, draws water into the tubule, increased water excretion but not much Na+ excreted

Question 12

What are some problems with osmotic diuretics?

Answer 12

Expands the extracellular fluid volume initially
Decrease blood viscosity
Inhibit renin release, increase renal blood flow

Question 13

When are osmotic diuretics used?

Answer 13

Acute renal failure due to shock or trauma
Acute drug poisoning
To decrease intracranial and intraocular pressure before ophthalmic or brain procedures

Question 14

What are some side effects of osmotic diuretics?

Answer 14

Headache, nausea, vomiting due to hyponatremia
Extracellular volume expansion, complicates heart failure and pulmonary oedema
Contraindicated in chronic heart failure
Excessive use leads to dehydration and hypernatraemia

Question 15

How do loop diuretics work?

Answer 15

Block Na+/K+/2Cl- co transporter
Reduce amount of Na+ reabsorbed
Very fast acting

Question 16

Give 2 examples of loop diuretics

Answer 16

Bumetanide

Furosemide

Question 17

When are loop diuretics used?

Answer 17

Severe oedema associated with congestive heart failure, nephrotic syndrome
Treatment for oliguric ARF
Treatment for hypercalcaemia
Acute pulmonary oedema
Acute hyperkalaemia 
Toxicity of Br, F, I

Question 18

What are the side effects of loop diuretics?

Answer 18

Hypovolemia
Hyponatraemia
Hypokalaemia
Hypomagnesaemia
Hypocalcemia
Metabolic alkalosis
Postural hypotension

Question 19

How do thiazides and thiazides like diuretics work?

Answer 19

Block Na+/Cl- co transporters, reducing amount of Na+ reabsorbed
First line antihypertensive

Question 20

What are the effects of thiazides and thiazide like diuretics on electrolyte composition of urine?

Answer 20

Increased urinary NaCl excretion
Increased urinary K excretion
Increased urinary magnesium excretion
Decreased calcium excretion
Decreased uric acid excretion

Question 21

What are thiazides used for?

Answer 21

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

Question 22

How do potassium sparing and aldosterone antagonist diuretics work?

Answer 22

Block aldosterone receptor, no increase in up regulation of ENaC channels and ROMK channels
Potassium sparing block K+ channels, no 3Na+/2K+ pump
Reduce reabsorption of sodium

Question 23

Give an example of a potassium sparing diuretic

Answer 23

Amiloride

Question 24

Give an example of an aldosterone antagonist diuretic

Answer 24

Spironolactone

Question 25

What are the uses for potassium sparing and aldosterone antagonists?

Answer 25

Secondary hyperaldosteronism
CHF, hepatic cirrhosis, nephrotic syndrome
Treatment of hypertension

Question 26

When is potassium sparing and aldosterone antagonists contraindicated?

Answer 26

In patients with hyperkalaemia and liver disease