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Metabolism 2 > Diuretics > Flashcards

Diuretics Flashcards

1
Q

what is the basic mechanisms of diruetics

A
  • they reduce the sodium reabsorption at different sites of the nephron
  • therefore they cause an increase in urinary sodium and water loss
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2
Q

What are the three ways in which the kidney handles sodium

A

Filtration
Reabsorption
Excretion

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3
Q

describe how the loop of Henle works

A

You take filtrates and the fluid comes down the loop of Henle and the descending walls are permeable to sodium and chloride, diffuse down there concentration gradient into the medulla and water follows down the concentration gradient
Makes the solute more concentrated therefore at the tip of the loop of henle it is most concentration
Then at the ascending limb the walls are water tight so water cant leave
Activate transport of sodium chloride and this dilutes the filtrate again and you end up with more dilute urine then what you started with

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4
Q

Name the 5 Different classes of diuretics

A 
Carbonic anhydrase inhibitors
Loop
Thiazide
Potassium sparing diuretics
Osmotic diuretics
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5
Q

what is an example of carbonic anhydrase inhibitor

A

Acetazolamide

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6
Q

How does a carbonic anhydrase inhibitor work as a loop diuretic

A

Normally
- In the proximal convoluted tubule have salt and water in the tubular lumen,
- normally bicarbonate joins with the hydrogen ions and forms H2CO3 this then dissociates into water and CO2 which diffuse into PCT cells,
- CA controls this,
in the cell this same reaction happens but in reverse - CA also controls this
- the hydrogen ions via a sodium hydrogen antiporter diffuse back into the lumen urine therefore for every hydrogen entering the lumen uirne sodium diffuses back into the proximal convulted tubule
- the bicarbonate diffuses back into the blood and is reabsorbed down the concentration gradient

Therefore a carbon anhydrase inhibitor blocks this action by preventing H2CO3 being converted inot H20 and CO2 and preventing CO2 and H20 converting back to H2CO3
- therefore either are no hydrogen ions for the sodium hydrogen antiporter therefore sodium does not diffuse into the proximal convoluted tubule and is excreted this causes water to be excreted

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7
Q

what is the main use of acetazolamide (carbonic anhydrase)

A
  • main use is not as a diuretic
  • glaucoma
  • epilepsy
  • mountain sickness - causes a metabolic acidosis to counteract respiratory alkalosis
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8
Q

what are the side effects of acetazolamide (carbonic anhydrase)

A

metabolic acidosis - contraindicated in significant CKD

  • sedation
  • sulphonamide antibiotics which can lead to bone marrow suppression
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9
Q

Name two types of loop diuretics

A

Frusemide

Bumetanide

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10
Q

How do loop diuretics work

A

= works in the thick ascending limb

  • Blocks the Na/K/2Cl
  • this means sodium remains in the urine therefore water reabsorption is inhibited
  • can also loose calcium and magnesium due to the need to maintain electroneutrality of the cell
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11
Q

what does loop direutics cause in terms of calcium and magensium

A

Hypocalemia
hypomagensium
- increase in these in the urine and decrease in the blood

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12
Q

what is the most potent direutic

A

loop diuretic

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13
Q

what does loop diuretics excrete

A

Excretion of potassium, sodium and water, calcium magnesium

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14
Q

when would you use a loop diuretic

A

Hypertension
Heart failure
Volume overload from CKD

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15
Q

What are the side effects of loop diuretics

A

Hypokalaemia

Dehydration…Acute renal failure

Kidney stones - high amount of calcium in the urine

Deafness- only in high doses

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16
Q

what are the examples of thiazides

A

Bendroflumethiazide
Hydrochlorothiazide

Thiazide like drugs: - do the same job of thiazide

  • Chlorthalidone
  • Indapamide
  • Metolazone
17
Q

Name some thiazide like diruetics

A

Thiazide like drugs: - do the same job of thiazide

  • Chlorthalidone
  • Indapamide
  • Metolazone
18
Q

How do a thiazide diuretic work

A

= works in the distal convoluted tubule

  • blocks sodium and chloride symporter
  • this prevents sodium entering the distal convulted tubule therefore prevents water reabsorption
19
Q

what is the effect of thiazide diuretics on calcium

A
  • cause hypercalemia as they cause calcium to enter the distal convulted tubule to maintian electroneutralisity thereofre they increase the amoutn of calcium being reasborbed in the blood
20
Q

what are thiazide used for

A
  • Primarily an antihypertensive

Effect beyond diuretic effects…

  • Reduction in plasma volume
  • Reduction in peripheral resistance
21
Q

what are the side effects of thiazide diuretics

A

Electrolyte effects:

  • Hypokalaemia
  • Hypercalcaemia
  • Hyponatraemia (particularly in old people)

Hyperglycaemia

Hypercholesterolaemia

22
Q

what are the two different types of potassium sparing direutics

A
  • epithelial sodium channel antagonists

- aldosterone antagonists

23
Q

name some examples of potassium sparing diuretics

A

Epithelial Na Channel antagonists

  • Amiloride
  • Triamterene

Aldosterone antagonists:

  • Spironolactone
  • Eplerenone
24
Q

How does epithelial sodium channel antagonists work (amiloride and triamterene)

A

= collecting tubule

  • it blocks the EnAC sodium reabsorption
  • this prevents sodium reasborption
  • this means that potassium isnt excreted in order to maintain electroneturality
25
Q

why do some diuretics end up with hypokalemia

A

In the collecting tubule there is a sodium channel and a potassium channel

  • the more sodium ions that are reabsorbed the more potassium ions that are excreted out of the collecting tubule in order to maintain the electroneutrlaitiy of the collecting tubule
  • therefore more potassium is excreted
  • thiazides cause more sodium lumen urine thereofre when you get to the collecting tubule more sodium is reabsorebd by the sodium channel thereofr ethis casues more potassium ions to be excreted
26
Q

what are the clinical uses of epithelial sodium channel antagonists work (amiloride and triamterene)

A

Heart failure

Hypokalaemia (from other diuretics)

  • Co-amilofruse (amiloride and fruesmodie)
  • Co-amilozide ( amiloride and thiazide)

Cirrhosis

27
Q

what are the side effects of epithelial sodium channel antagonists (amiloride and triamterene)

A

Hyperkalaemia

Hyponatraemia

28
Q

How do aldosterone antagonists work (spironolactone)

A
  • they prevent aldosterone from acting -
    take a bit of time to work
  • this prevents the insertion of sodium EnAC channels
  • therefore prevents sodium reabsorption and excrete less potassium
29
Q

what are the uses of aldosterone antagonists work (spironolactone)

A

Hyperaldosteronism (Conns)

Heart failure

Hypokalaemia (from other diuretics)

Cirrhosis

30
Q

What are the side effects of aldosterone antagonists work (spironolactone)

A

Hyperkalaemia
Gynecomastia (not eplerenone)
Hyponatraemia (Cirrhosis)

31
Q

How do osmotic direusis work

A
  • any osmotically active molecule that is freely filtered in the glomerulus and is not reabsorbed by the tubules e.g. not clincially (glucose)
  • this works by water reasborption
  • it also reasborbs sodium potassium and urea
32
Q

what is the most clinical osmotic diuresis

A

Mannitol

33
Q

when can osmotic diuretics be used

A

Cerebral oedema - causes fluid to go out of the interstitial tissues and into the blood leading to excretion of fluid and stopping brain swelling

Oliguric acute renal failure

34
Q

What are the side effects of osmotic diuresis

A

Transient fluid overload
- Pulmonary odema

Other non pharmacological osmotic diuretics

  • Glucose- DKA/HHS
  • Urea - Disequilibrium syndrome
35
Q

When do you not use diuretics

A

When hypotensive – make blood pressure worst

When dehydrated – don’t want to loose more fluid

When hypokalaemic (Loop/Thiazide) – loop potassium should stop loop and thiazide

When hyperkalaemic (Amiloride, aldosterone antagonists) – stop potassium sparing direutics

Post surgery, with a poor urine output – need to give fluids and not diuretics – people who have had surgery and pass less urine don’t make it artificial with diuretics

Metabolism 2 (40 decks)

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