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Pharmacology B > Lecture 1 - Diuretics > Flashcards

Lecture 1 - Diuretics Flashcards

1
Q

What are the thiazide diuretics?

A

hydrochlorothiazide
chlorthalidone
metolazone

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2
Q

What are the loop diuretics?

A

furosemide

ethacynic acid

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3
Q

What is a potassium sparing diuretic?

A

spironolactone

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4
Q

Thiazide, loop, and potassium sparing diuretics are _______ diuretics

A

classic

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5
Q

Other than classic diuretics what is the other group of diuretics?

A

solute and/or water excretion altering (not clinically used as diuretics)

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6
Q

_____ = osmotic diuretic

A

mannitol

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7
Q

______ = carbonic anhydrase inhibitor

A

acetazolamide

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8
Q

_______ = vasopressin receptor antagonist

A

tolvaptan

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9
Q

_______ = sodium/glucose co-transport 2 inhibitor

A

dapagliflozin

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10
Q

Definition of a diuretic?

A

agents which increase urine flow

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11
Q

Clinically, what do diuretics do?

A
  • renal solute excretion (sodium and water)

- block sodium reabsorption and water will follow later

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12
Q

Aim of therapy for diuretics?

A
  • only need to decrease sodium reabsorption a few %

- change of 5% has a great effect

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13
Q

How much % of Na is reabsorbed?

A

99.6%

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14
Q

How many mmol/day of Na is excreted?

A

100

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15
Q

If Na reabsorption decreases to 95% then ____ mmol/day of Na is excreted

A

1250

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16
Q

Where does dapagliflozin work?

A

blocks glucose and sodium reabsorption (so it’s excreted, and then water will follow and be excreted as well)

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17
Q

Where does mannitol work?

A

increases H2O excretion

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18
Q

Where does acetazolamide work?

A

Increases excretion of HCO3

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19
Q

Where does hydrochlorothiazide and metolazone work?

A

increase NaCl excretion

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20
Q

Where does furosemide work?

A

Increases Na, Cl, and K excretion and Mg, Ca will follow

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21
Q

Where does spironolactone work?

A

blocks Na reabsorption

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22
Q

Where does tolvaptan work?

A

ADH (vasopressin receptor antagonist)

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23
Q

make fucking sense of slide 5 and 6

A

kay

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24
Q

Where do thiazide diuretics work?

A

In distal tubule (primary site of action) to:

  • Increase NaCl excretion (decrease reabsorption)
  • Decrease Ca excretion (increase reabsorption) - loop diuretics do the opposite

*they have some proximal tubular effect but it is not normally important (it is only important when combined with loop diuretic)

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25
Q

____ diuretics - may decrease blood pressure without a perceivable volume loss, low dose is usually effective (with decreased toxicity)

A

thiazide

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26
Q

For elderly patients, ____ diuretics are a problem

A

loop
*Because they increase the calcium excretion (decrease the Ca reabsorption) and can contribute to osteoporosis or other bone diseases

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27
Q

What is the formula for BP?

A

BP = CO x TPR

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28
Q

Describe how thiazide diuretics decrease blood pressure

A
  • increase NaCl excretion
  • decrease blood volume
  • decreases cardiac output (which decreases BP - think of the BP formula)
  • apparent tolerance = no diuresis?
  • blood volume and CO returns to normal
  • blood pressure stays down and may decrease further
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29
Q

Problems with thiazide diuretics?

A
  • *in addition to electrolyte problems
  • increased incidence of other risk factors for CV disease
    • hyperglycemia (decreased insulin release, decreased tissue utilization)
    • increased LDL levels (must monitor)
  • increased incidence of ED
  • plasma volume contraction due to increased urine loss
    • increased proximal tubule reabsorption, response to fluid loss
    • increased lithium; urea reabsorption
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30
Q

What are thiazide diuretics used for?

A
  • edema

- hypertension

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31
Q

Advantages of thiazide diuretics?

A
  • orally active, low toxicity, no postural hypotension

- potentiate other antihypertensive drugs

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32
Q

____ diuretics include furosemide, bumetanide, ethacrynic acid (non sulphonamide)

A

Loop

33
Q

___ _____ diuretics are very potent and efficacious

A

high ceiling

34
Q

Why are high ceiling diuretics dangerous?

A

up to 20% of filtered load excreted

35
Q

Loop diuretics:

____ and ____ application

A

oral

IV

36
Q

Loop diuretics:

Increase _____ production which results in vasodilation

A

prostaglandin

37
Q

Where are loop diuretics useful?

A

in acute pulmonary edema - because it vasodilators veins

38
Q

___ may decrease function of loop and thiazide diuretics

A

NSAIDs

39
Q

MOA of loop diuretics?

A
  • increases Na, Cl, and K excretion and Mg, Ca follow (excreted)
  • inhibits renal diluting ability and abolishes the renal concentrating ability, urine becomes isotonic or slightly dilute
40
Q

Problems with loop diuretics?

A
  • in addition to electrolyte imbalances
  • deafness - never combine with aminoglycoside antibiotics
  • chronic dilution hyponatremia (due to excrete of an isotonic urine)
41
Q

Uses of loop diuretics?

A
  • good in renal insufficiency (GFR < 50 mL/min)

- edema (pulmonary); hypertension (not as sole medication); hypercalcemia (opposite to thiazides); heart failure

42
Q

What do you need to caution if a patient is not responding to a loop diuretic? And how do you manage it?

A
  • caution regarding circulating chloride concentration
  • add a thiazide diuretic
  • metolazone often used for this
43
Q

What is the main electrolyte problem with thiazide and loop diuretics?

A

Potassium depletion

  • not a problem in healthy patients
  • more a problem if low potassium already a problem (heart failure, cirrhosis, etc.)
44
Q

What are the two major causes of potassium depletion?

A

1) Secondary hyperaldosteronism (due to plasma volume depletion)
- increased renin
- increases angiotensin 2
- increased aldosterone
- Na reabsorption at expense of K (and H) loss

2) Increased Na delivery from distal tubule
- due to inhibition of Na reabsorption in loop and distal tubule
- collecting tubules therefore increase Na reabsorption - to conserve sodium

45
Q

Describe the potassium depletion treatment

A

1) dietary intake - apricots and bananas
2) potassium chloride tablets - chloride salt - dilute solution
3) slow - potassium tablets - ulceration
4) emergencies require IV KCl - repeat cautiously until potassium rises
5) potassium sparing diuretics
- weak diuretics
- give with other diuretics to decrease K loss
- may cause hyperkalemia

Never coming potassium sparing diuretics with K supplements

46
Q

List 3 potassium sparing diuretics

A
  • spironolactone
  • triamterene
  • amiloride
47
Q

How does spironolactone work?

A
  • blocks aldosterone receptor

- prevents cardiac remodelling (fibrosis, cardiac collagen proliferation) - may delay progression of failure

48
Q

How does triamterene and amiloride work?

A

-decreases sodium permeability

49
Q

B-blockers, ACEi’s and ARB’s may also increase plasma _____ concentrations

A

potassium

50
Q

B-blockers decrease potassium _____ cells

A

entering

51
Q

ACEi’s and ARB’s decrease ______ concentrations

A

aldosterone

52
Q

So potassium depletion is one electrolyte disturbance, what is another?

A

Extracellular Volume Depletion

  • furosemide - kidney unable to concentrate or dilute
  • excrete an isotonic urine
  • inability to concentrate urine (save water)
    • simply drink more water to excrete solutes
  • inability to dilute urine (excrete excess water)
    • ingest hypotonic solution - excrete isotonic urine
    • net loss of electrolytes including plasma sodium
    • chronic dilution hyponatremia
53
Q

Describe calcium as an electrolyte disturbance

A
  • Thiazides decrease calcium excretion, good for hypocalciuria
  • Furosemide increases calcium excretion, good for hypercalcemia
54
Q

Describe how volume depletion and increased proximal tubule reabsorption can be a problem.

A

1) uric acid excretion
- initially increased but decreased with chronic administration (gout?)

2) Lithium - increased proximal tubular reabsorption
- toxicity is a concern (same clinical concern for digoxin)

55
Q

List the 4 uses of diuretics

A
  • tissue edema
  • hypertension
  • hepatic cirrhosis
  • cardiac failure
56
Q

Describe how diuretics treat tissue edema

A
  • fluid shift into the extracellular space has exceeded 3 to 4 L due to salt and water retention
  • Loop diuretic (furosemide) preferred
  • if no response to loop diuretic, check for low serum chloride concentration
  • fluid excreted in urine is taken from the “vascular space”, allow time for this to be replaced by the interstitial (oedematous) fluid - go slow! otherwise CV collapse
57
Q

Describe how diuretics treat hypertension

A
  • 1st line single therapy (thiazide diuretic)
  • but possible increase in LDL and plasma glucose (not metabolically neutral)
  • good as second medication to treat sodium and water retention
  • which is a common side effect of other anti-hypertensives
58
Q

Describe how diuretics treat hepatic cirrhosis

A
  • sodium/water accumulates in the abdomen and/or tissue
  • abdominal fluid movement into vascular space may be a concern
  • slower than fluid movement from interstitial to vascular space
  • aggressive treatment will remove fluid faster from the vascular space than can be replaced fly the abdominal fluid
59
Q

Describe how diuretics treat cardiac failure

A
  • fluid retention increases vascular volume
  • helps to increase preload and stimulate the heart
  • as failure continues so does fluid retention
  • preload increases to levels causing edema
  • diuretics decrease vascular volume
  • successful treatment of heart failure requires adequate control of vascular volume
60
Q

What are osmotic diuretics?

A

osmotically active compounds in the plasma

61
Q

List 4 properties for a perfect osmotic diuretic

A
  • filtered
  • not reabsorbed
  • pharmacologically inert
  • resistant to alteration

*osmotically active compounds “hold” onto water - high urine volume - little sodium

62
Q

List 3 uses of mannitol (IV) and glycerol (oral)

A
  • vascular surgery
  • renal transplant
  • ophthalmological procedures
63
Q

Where do osmotic diuretics work?

A

they block water reabsorption so they increase water excretion

64
Q

What is an example of a carbonic anhydrase inhibitor?

A

Acetazolamide (Diamox)

65
Q

Describe carbonic anhydrase inhibitors (ex. acetazolamide)

A
  • very weak diuretics
  • inhibit carbonic anhydrase
  • decreases reabsorption of bicarbonate in proximal tubular cells
  • increase bicarbonate excretion (with some sodium)
66
Q

Uses of carbonic anhydrase inhibitors (ex. acetazolamide)

A
  • in severe alkalosis (increases renal excretion of bicarbonate)
  • alkalinization of filtrate ionizes acidic drugs
  • ionization increases renal excretion ex. salicylate
67
Q

List 3 main uses of carbonic anhydrase inhibitors (ex. acetazolamide)

A
  • acute mountain sickness
  • increasing excretion of weak acids
  • glaucoma - decreases aqueous humor formation
68
Q

MOA of carbonic anhydrase inhibitors (ex. acetazolamide)

A

increase renal excretion of bicarbonate

69
Q

Conivaptan is a ????

A

ADH Antagonist

70
Q

ADH (vasopressin) increases water _____ (no effect on electrolytes)

A

reabsorption

71
Q

How does conivaptan work?

A

Blocks the ADH receptor in the collecting tubules

*Increases water excretion without electrolytes

72
Q

____ is increased in heart failure and syndrome of inappropriate ADH (SIADH) secretion. The chronic increased water reabsorption may produce ______.

A

vasopressin (ADH)

hyponatremia (diluted sodium)

73
Q

What can ADH antagonists produce?

A

nephrogenic diabetes insipidus (increased urine flow due to lack of a renal effect of ADH)

74
Q

Main uses of conivaptan (ADH antagonist)

A

SIADH (relatively new)

75
Q

MOA of ADH antagonists

A

block ADH receptors, increase water excretion

76
Q

Dapagliflozin is a ??

A

Sodium glucose Co-transport 2 (SGLT2) inhibitor

77
Q

What is sodium glucose co-transport 2?

A

the major site of glucose reabsorption in the proximal tubule

90% is via the SGLT2

blockade of this transport increases urinary excretion of glucose
*associated with a small decrease in plasma glucose

78
Q

SGLT2 inhibitors associated with?

A

a decrease in blood pressure and weight

Pharmacology B (21 decks)

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