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PHARMACOLOGY SEMMELWEIS > Diuretics > Flashcards

Diuretics Flashcards

1
Q

Classification of Diuretic drugs

A
  1. Carbonic anhydrase inhibitors in PCT
  2. Osmotic diuresis (‘aquaretic’) in entire tubule
  3. Loop diuretics in Ascending limb
  4. Thiazide diuretics in early distal
  5. K sparing in early collecting
  6. Aldosterone antagonists in early collecting
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2
Q

What are the K+ excreting diuretics?

A

CA inhibitors, loop diuretics, and Thiazides are K+ excreting diuretics

  • incresing HCO3- concentration in collecting tubule
  • incresingNa+ concentration in collecting tubule
  • increasing Aldosterone secretion (secondary hyperaldosteronism)
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3
Q

Mechanism of CA inhibitors

A

Inhibition of carbonic anhydrase enzyme [CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-] - Diuresis (loss of NaHCO3 in the proximal convoluted tubule) – self-limiting process within 2-3 days - Metabolic acidosis (due to bicarbonate depletion) - K+ wasting (excess Na+is reabsorbed in the collecting tubule in exchange for K+ excretion)

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4
Q

2 CA inhibitors

A

Acetazolamide (B22), Dorzolamide (not in the list)

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5
Q

Acetazolamide (B22), Dorzolamide (not in the list) - Mode of action

A
  • Renal
    1. Inhibition of CA in proximal convoluted tubule -> prevents the formation of HCO3- and H+
  • decreasing HCO3- and Na+ reabsorption
  • Alkalic urine (increasing pH)
  • Metabolic acidosis
  • increasing K+, Ca2+, Pi excretion
  • Diuresis
  1. Delayed consequences:
  • decreasing plasma HCO3- -> decreasing HCO3- filtration -> decreasing Na+ excretion -> decreasing diuresis
  • increasing H+ secretion due to acidosis -> acidic urine
  • Tolerance (after 1wks): decreasing plasma HCO3-> decreasing filtrated HCO3 -> decreasing Na loss -> decreasing water loss
  • Extrarenal
    1. decreasing production of aqueous humor
    2. decreasing production of CSF
    3. decreasing production of gastric and pancreatic juice
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6
Q

Acetazolamide (B22), Dorzolamide (not in the list) - Indication

A
  1. Glaucoma

• It causes decreasing production of aqueous humor and decreasing intraocular pressure in patients with chronic open-angle glaucoma.

  • Probably by blocking CA from ciliary body of the eye
    2. Acute mountain sickness prophylaxis

• It prevents weakness, breathlessness, dizziness, nausea, cerebral and

pulmonary edema.

  1. Metabolic alkalosis
  2. Urinary alkalization
    * E.g. aspirin poisoning
  3. Severe hyperphosphatemia
  4. Adjacent therapy:
  • Epilepsy
  • Refractory edema (doesn’t respond to normal diuretic treatment)
  • CSF leakage
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7
Q

Acetazolamide (B22), Dorzolamide (not in the list) - Pharmacokinetics and Adverse effects

A
  1. Pharmacokinetics
  • 90% protein bound
  • Renal elimination (active tubular
    secretion + passive reabsorption)
  • Administration:
    • Oral
    • IV
  1. Adverse effects
  • Hyperchloremic metabolic acidosis
  • Hypokalemia
  • Paresthesia
  • Somnolence
  • Renal stones (Ca-phosphate, cysteine)
  • BM suppression
  • Hypersensitivity reactions (sulphatecontaining
    drugs)
    Contraindications:
  • Sulphonamide sensitivity
  • Severe kidney and/or hepatic
    disorders
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8
Q

4 osmotic diuretics

A

Glycerol (B23), Mannitol (B23), Isosorbide (not in the list), Urea (not in the list)

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9
Q

Glycerol (B23), Mannitol (B23), Isosorbide (not in the list), Urea (not in the list)

-Mode of action

A
  1. They increases osmolarity in the tubular fluid and
    prevent further water reabsorption -> osmotic diuresis
  2. Hyperosmosis in the blood ->increasing EC volume -> increasing GFR
  3. decrasing ADH secretion
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10
Q

Glycerol (B23), Mannitol (B23), Isosorbide (not in the list), Urea (not in the list)

-Indication, side effects, and contraindication

A

Indication

  1. Brain edema : urea and mannitol infusion
  2. Acute kidney failure (shock kidney) : Mannitol infusion with loop diuretics
  3. Refractory edema (when it is induced by kidney or liver disorders)
  4. Glaucoma (acute severe- Glaucoma attack)
  5. Cystic fibrosis (mannitol spray)

Side effects

Heart failure, increased extracellular fluid volume (too strong osmotic effects), hyponatremia

Contraindication

Liver cirrhosis, Heart failure

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11
Q

4 Loop diuretics

A

Etacrynic acid (B22)
Furosemide (B22)
Bumetanide (not in the list)
Torsemide (not in the list)

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12
Q

Mode of action

Etacrynic acid (B22)
Furosemide (B22)
Bumetanide (not in the list)
Torsemide (not in the list)

A

It blocks NKCC2 in the TAL:

  • Na+ and K+ stay in the TAL -> diuresis
  • Negative potential (as K+ doesn’t leak out) -> increasing Ca2+
    and Mg2+ excretion
  • decreasing osmotic gradient
  • decreasing uric acid secretion
  • Deceit of macula densa (due to decreasing Na+ inside juxtaglomerular cells):
    • increasing COX2 expression -> increasing PGE2
  • increasing renin release
  • increasing RBF
  • decreasing ¯ pulmonary congestion
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13
Q

Indication

Etacrynic acid (B22)
Furosemide (B22)
Bumetanide (not in the list)
Torsemide (not in the list)

A

1. Acute pulmonary edema (LV failure)
• Improvement of venous tone
2. Congestive heart failure
3. Refractory edema
4. Acute/chronic kidney failure
5. Hypertension
• Not 1st line
• In the case of impairment of kidney function
6. Poisoning (forced diuresis)
• E.g. Br, Fl, J (not Li!!!)
• Risk of dehydration if the fluid is not replenish, thus usually given
with an infusion

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14
Q

Pharmacokinetics and Adverse effects

Etacrynic acid (B22)
Furosemide (B22)
Bumetanide (not in the list)
Torsemide (not in the list)

A
  1. Pharmacokinetics
    - Furosemide :
  • taken orally(only 50% is absorbed) or i,v
  • 20-80mg in the morning

-Torsemide

  • taken orally, better absorption, fast
  • 2.5-20mg

-Bumetanide

  • taken orally, 40times potent than furosemide, fast, short duration of action
  • 0.5- 2mg
  1. Adverse effects
    - Hypokalemia, Hypocalcemia, Hyperuricemia, Hyperuricemia
  • Hypovolemia, Hypomagnesemia
  • Metabolic alkalosis
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15
Q

2 Thiazides and 4 related compounds (one each in the list)

A

Thiazides:
Bendroflumethiazide (not in the list)
Hydrochlorothiazide (B22)

Related compounds:
Indapamide (B22)
Clorthalidone (not in the list)
Metolazone (not in the list)
Clopamide (not in the list)

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16
Q

Thiazide - mode of action

A

Inhibits Na+ and Cl- transporters in DCT

  • increasing Na+ and Cl- excretion
  • increasing K+ and Mg2+ excretion
  • increasing Ca2+ absorption -> Hypercalcemia

Stimulation of luminal PTH-dependent Ca2+ channel as there is decreasing Na+ inside the cell -> increasing activity of Na+/Ca2+ antiporter

Consequences

Diuretic

Hypokalemia, hypomagnesomia

Metabolic alkalosis

Hypercalcemia

17
Q

Thiazide Indication

A
  • *- Congestive heart failure
  • Hypertension (1st line)
  • Edema
  • Idiopathic hypercalciuria (kidney stones)
  • Nephrogenic diabetes insipidus**
18
Q

4 potassium sparing diuretics (3 in the list)

A

Spironolactone (B23)

Eplerenone (B23)

Amiloride (B23)

Triamterene (not in the list)

19
Q

What are the two aldosteron receptor antagonists?

A

Spironolactone and Eplerenone

20
Q

Mode of action of aldosteron receptor antagonists

A
  • Aldosterone acts on these cells. It is released in hyponatremia, hyperkalemia or due to renin release.
  • It can induce the expression of different genes:
    o ENaC -> increasing [Na+]IC -> increasing IC potential -> K+ efflux to tubular lumen
    o Na+/K+ or Na+/H+ antiporters -> Na+ + water retention and K+, H+ will be excreted.
    o Na+/K+ ATPase
  • These K+-sparing diuretics can affect the aldosterone receptor.

Aldosterone receptor antagonists:

Spironolactone, Eplerenone
- Inhibition of the expression of aldosterone dependent
Na+/K+ ATPase and Na+ transporters (Na+/K+ or Na+/H+ antiporters)
• Na+ excretion -> diuresis
• K+ reabsorption increasing

21
Q

Indication of Aldosteron receptor antagonists

A

-Primary hyperaldosteronism (Conn’s syndrome)
- Secondary hyperaldosteronism
• Congestive heart failure
• Liver cirrhosis
• Nephrosis
- Hypertension (not really used)

22
Q

Pharmacokinetics of potassium sparing diuretics

A
  1. Spironolactone
  • orally administered
  • Aldactazide : spironolactone/Thiazide combo
  1. Amiloride
  • orally adminstered, 50 % effective
  • not metabolized
  • not bound to plasma proteins
  1. Triamterene
  • orally administration, 50% effective
  • 60% bound to plasma proteins
  • liver metabolism, active metabolites
23
Q

What are the drugs that can inhibit ENaC

A

Amiloride (B23)
Triamterene (not in the list)

24
Q

Mode of action

Amiloride (B23)
Triamterene (not in the list)

A

Inhibition of ENaC:
- decreasing Na+/K+ exchange ->
• Na+ excretion
• Diuresis
• Ø K+ loss

25
Q

4 ADH antagonists ( 1 in the list)

A

Li+ salts (not in the list)
Demeclocycline (not in the list)
(tetracycline derivative)

Conivaptan (not in the list)
Tolvaptan (B23)

26
Q

Mode of action

ADH antagonists

A
  1. Li+ salts (not in the list), Demeclocycline (not in the list)
  • Inhibition of cAMP-mediated processes
  • SIADH, Hyponatremia
  • Metabolized in the liver
  • Nausia, Thirst, Polyuria, Dehydration, Hypoglycemia
  1. Conivaptan (not in the list), Tolvaptan (B23)
  • ADH (V2) antagonists
  • SIADH, Hyponatremia
  • Metabolized in the liver
  • Nausia, Thirst, Polyuria, Dehydration, Hypoglycemia
27
Q
A

PHARMACOLOGY SEMMELWEIS (54 decks)

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