6) Diuretics

Question 1

Describe the mechanism of action of Carbonic Anhydrase inhibitors

Answer 1

Works at the PCT

> Prevent re absorption of Na+ with bicarbonate

Question 2

What ADRs can occur with Carbonic Anhydrase Inhibitors ?

Answer 2

> Because of reduced bicarbonate re absorption, patients will become Acidotic
Hypokalaemia, increase ENac activity => K+ loss at CD

Question 3

When are Carbonic Anhydrase Inhibitors used ?

Answer 3

It is used to treat Glaucoma

Question 4

Describe the mechanism of action of Osmotic Agents e.g. Mannitol

Answer 4

They ensure that water remains in the Lumen of the tubule.

> Works at the PCT

Question 5

What ADRs can occur with Osmotic Agent ?

Answer 5

> Reduced Intracellular volume

> Risk of Hypernatraemia

Question 6

When are Osmotic Agents used ?

Answer 6

Swellings in the brain

Question 7

What is the mechanism of action of Loop Diuretics?

> Example

Answer 7

Blocks NKCC2 in the Loop of Henle, this leads to an increase in Na+ and thus water excretion
> Furosemide

Question 8

What ADRs can occur with Loop Diuretics ?

Answer 8

> Hypocalcaemia, 
> Ototoxicity 
> Alkalosis 
> Hypokalaemia 
> Increased LDL 
> Gout

Question 9

Describe the mechanism of action of Thiazides

Answer 9

Blocks NCCT channel in the DCT inhibiting NaCl re absorption

Question 10

What ADRs can occur with Thiazides

Answer 10

> Gout 
> Hyperglycaemia 
> Increased LDL 
> Hypercalcaemia 
> HypoKalaemia

Question 11

Describe the mechanism of action of Amiloride ?

Answer 11

Blocks ENaC in the collecting duct

> It is a potassium sparing diuretic

Question 12

Describe the mechanism of action of Spironolactone ?

Answer 12

Acts as a Aldosterone Antagonist.

> Potassium Sparing Diuretic

Question 13

What are some ADRs of Spironolactone ?

Answer 13

> Hyperkalaemia
Impotence
Painful Gynaecomastia

Question 14

What is the mechanism of action ADH Antagonists (Aquaretics)
> Example ?

Answer 14

> Inhibits the action of ADH
Causes diuresis but not natriuresis
Tolvaptan
Lithium

Question 15

When may ADH Antagonists be used ?

Answer 15

> APCKD

> Patient has Hyponatraemia

Question 16

Name two other substances which have diuretic action ?

Answer 16

> Alcohol , prevents ADH release

>Caffeine, increased GFR and reduced Na re absorption

Question 17

List General Adverse Drug Reactions of Diuretics

Answer 17

> Anaphylaxis 
> Hypovolaemia 
> Hypo tension 
=> Leading to AKI and RAAS activation 
> Electrolyte Imbalance 
> Metabolic Abnormalities e..g Acidosis 
> Be careful when co prescribing with other drugs such as ACEi, Digoxin, B-Blockers and Steroids

Question 18

What Patient factors may lead to Diuretic Resistance

Answer 18

> Gut Oedema e.g. in Nephrotic Syndrome this means that the drug cannot be absorbed and thus may need to be given IV

> Heart Failure - Blood isn’t pumped adequately to the kidney so the drug isn’t delivered there, thus may need to increase

> Liver Problems - Certain drugs such as furosemide rely on albumin for distribution

> Kidney Problems

> Salt intake

Question 19

What diuretic do you use to treat Hypertension ?

Answer 19

> Thiazides - Act as Vasodilators as well
Spironolactone (loop diuretic)
- Choose if cause is Primary Hyperaldosteronism

Question 20

What diuretic do you use to treat Heart Failure ?

Answer 20

> Loop diuretics - does not affect BP

Question 21

What diuretic do you use to treat Liver Disease ?

Answer 21

> Spironolactone

> Loop Diuretics

Question 22

What diuretic do you use to treat Nephrotic Syndrome ?

Answer 22

> Loop Diuretic High Dose

> + Thiazide if no improvements