9. Pharmacology of Diuretics

Question 1

What are the four different types of diuretics?

Answer 1

Osmotic Diuretics
Loop Diuretics
Thiazide
Potassium sparing diuretics

Question 2

Where do osmotic diuretics act?

Answer 2

PCT

Question 3

What do osmotic diuretic do?

Answer 3

Reduce H20 reabsorption

Reduce electrolyte reabsorption

Question 4

What are side effects of osmotic diuretics?

Answer 4

Hypotension

Fluid and electrolyte disturbance

Question 5

Define the term diuretic

Answer 5

Causing increased passing of urine

Question 6

What is an example of carbonic anhydrase inhibitor?

Answer 6

Acetazolamide

Question 7

What is the mode of action of acetazolamide?

Answer 7

Inhibits carbonic anhydrase in PCT

Reduces Na+ and HCO3- reabsorption

Question 8

What are carbonic anhydrase inhibitors used for clinically?

Answer 8

Glaucoma and acute altitude sickness

Question 9

What are adverse effects of cabonic anhydrase inhibitors?

Answer 9

Metabolic acidosis
Hypokalaemia
Renal stone formation

Question 10

Examples of loop diuretics?

Answer 10

Furosemide, bumetanide torasemide

Question 11

How are loop diuretics given?

Answer 11

Orally or i.v.

Question 12

What do loop diuretics do?

Answer 12

Bind to proteins in plasma, limiting glomerular filtration

Secreted into tubular lumen by PCT cells via organic anion transporters

Question 13

What is the mode of action of loop diuretics?

Answer 13

Inhibit Na+/K+/2Cl- cotransopter in ascending limb of Loop pf Henle

Decrease osmolarity of medullary interstitium leading to decrease reasbsporption of water from collecting duct

Increase in excretion of Ca2+ and Mg2+ occurs becuase of inhibition of paracellular diffusion

Question 14

When are loop diuretics used clinically?

Answer 14

Congestive heart failure 
Resistant hypertension 
Liver ascites 
Nephrotic syndrome
Acute hypercalcaemia

Question 15

What are adverse effects of loop diueretics?

Answer 15

Hypovolaemia and dehydration 
Hypokalaemia 
Hypomagnesaemia 
Hyponatraemia 
Hyperuricaemia 
Oto and renal toxicity 
Allergic reactions to skin and kindey

Question 16

What happens when loop diuretics interact with thiazide diuretics?

Answer 16

Increased risk of electrolyte disturbance

Question 17

What happens when loop diuretics interact with aminoglycoside antibiotics?

Answer 17

Increased oto and nephrotoxicity

Question 18

What happens when loop diuretics interact with ACE inhibitor and other vasodilator drugs?

Answer 18

Risk of hypotension

Question 19

What happens when loop diuretics interact with non-steroidal anti-inflammatory drugs ?

Answer 19

Impaired diuresis

Question 20

What is the mode of action of thiazides in the early distal convoluted tubule?

Answer 20

Increase excretion of Na+ and Cl- by inhibiting Na+/Cl- cotransporter

Reabsorption of Ca2+ is increased due to stimulation of Na+/Ca2+ counter- transport as consequence of increased conc grad. for Na+ across basolateral membrane

Question 21

When are thiazide diuretics used clinically?

Answer 21

Uncomplicated hypertension
Occasionally in resistant oedema in heart failure or other causes of oedema
Protective in osteoporosis and for prevention of calcium renal stones

Question 22

What are the adverse effects of thiazide diuretics?

Answer 22

Same as loop but

> urate retention
increase in cholersterol and hypergylceamia
Reduced calcium excretion
Less oto and nephrotoxicity in combination with aminoglycosides

Question 23

What are the interactions with thiazide diuretics?

Answer 23

Same as a loop with a few exceptions

Question 24

What are the interactions of thiazide diuretics and ACE inhibitors?

Answer 24

Hypotension less likely

Question 25

What are the interactions of thiazide diuretics and lithium?

Answer 25

More likely to cause lithium toxicity

Question 26

What are the interactions of thiazide diuretics and SSRI anti-depressants?

Answer 26

More likely to cause hyponatraemia

Question 27

Where do potassium sparing diuretics act?

Answer 27

Action localised to late DCT/early collecting duct

Question 28

Examples of potassium sparing diuretics?

Answer 28

Soidium channel blockers | Aldosterone receptor antagonists

Question 29

What is the mode of action of amiloride and triamterine in late distal tubule and collecting duct?

Answer 29

Block apical Na+ channels Decrease in potential difference across principal cell Decrease driving force for K+ secretion from principal cell and H+ from intercalated cell Leading to increase Na+ excretion and decrease K+ and H+ excretion

Question 30

What is the mode of action of aldosterone antagonists in late distal tubule and collecting duct?

Answer 30

Alderstone - steroid hormone that acts on a nuclear receptor to increase synthesis of proteins which activate silent Na+ channels Increase synthesis of K+ channels ....look at this

Question 31

What blocks effects of aldosterone and what happens?

Answer 31

Spironolactone Eplerenone Leading to the increase of Na+ excretion and decrease in K+ and H+ excretion

Question 32

When are potassium sparing diuretics used clinically?

Answer 32

Used to prevent thiazide or loop diuretic- induced hypokaleamia

Question 33

When is spironolactone prescribed?

Answer 33

In conditions associated with primary and secondary hyperaldosteronism

Question 34

Adverse effects of potassium sparing diueretics?

Answer 34

Hyperkalaemia Metabolic acidosis Gynaecomastia, impotence and testicular atrophy, menstrual irregularities

Question 35

Hyperkalaemia occurs when potassium-sparing diuretics interact with what?

Answer 35

``` ACE inhibitors Angiotensin II receptor antagonists Renin inhibitors Beta adrenoceptor antagonists Non steroidal anti-inflammatory drugs ```

Question 36

Are diuretics routine treament for renal failure?

Answer 36

No

Question 37

What should be used if chronic kidney disease with associated oedema is present?

Answer 37

Use loop diuretics with caution