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4 - CPT > Diuretics > Flashcards

Diuretics Flashcards

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1
Q

List drugs that act on renal tubules

A
  • Carbonic anhydrase inhibitors
  • Osmotic diuretics
  • Loop diuretics
  • Thiazides
  • Potassium sparing diuretics
  • Aldosterone antagonists
  • ADH antagonists
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2
Q

Describe the uses of carbonic anhydrase inhibitors

A
  • Eg. Acetazolamide
  • Used to treat glaucoma and altitude sickness
  • Not useful at inducing diuresis, as preventing Na reabsorption in PCT will cause greater Na reabsorption downstream
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3
Q

Describe the ADRs of carbonic anhydrase inhibitors

A
  • Decreasing bicarbonate reabsorption leads to metabolic acidosis
  • Renal stones
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4
Q

Describe the use of osmotic diuretics

A
  • Eg. Mannitol
  • Used to reduce high intracerebral pressure
  • Increase osmotic gradient throughout nephron to reduce water reabsorption
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5
Q

List the ADRs of osmotic diuretics

A

Allergic reactions, hypernatraemia, nausea, vomiting, dehydration

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6
Q

Describe the uses and mechanism of loop diuretics

A
  • Used to treat oedema (+/- hypertension in advanced CKD)
  • Mechanism
    • Inhibit NaKCC in the thick ascending limb of loop of Henle to decrease Na reabsorption
    • Reduces Ca and Mg reabsorption as well
    • Increased Na levels in the nephron means more Na is reabsorbed in the collecting duct, leading to more K secretion causing hypokalaemia
  • Decreased sodium reabsorption from loop diuretics reduces osmolarity gain in interstitium
    • Means RAAS and ADH effects aren’t able to absorb as much water as osmolarity in interstitium lower
      • Thiazide do not affect interstitium osmolarity
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7
Q

Describe the ADRs for loop diuretics

A
  • ADR for furosemide - ototoxicity, alkalosis, increase LDL, gout (increased urate), hypokalaemia
  • ADR for bumetanide - myalgia, alkalosis, hypokalaemia
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8
Q

Describe the uses and mechanism of thiazides

A
  • Eg. Bendroflumethiazide, indapamide
  • Used to treat hypertension
  • Mechanism
    • Inhibits NaCl co-transporter in the distal convoluted tubule
    • Promotes Ca reabsorption as K channels leak K back into the lumen, creating a positive luminal force
    • Increased Na levels in the nephron means more Na is reabsorbed in the collecting duct, leading to more K secretion causing hypokalaemia
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9
Q

List the ADRs of thiazides

A

Gout, hyperglycaemia (problem for diabetics), erectile dysfunction, increase LDL, hypercalcaemia, impotence

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10
Q

Describe the uses and mechanism of potassium sparing drugs

A
  • Eg. Amiloride
  • Used to treat hypokalaemia where diuretic is required
  • Mechanism
    • Inhibits ENac in the collecting duct to reduce Na reabsorption
  • Decreases K secretion leading to hyperkalaemia
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11
Q

List the ADRs of aldosterone antagonists

A

Hyperkalaemia, painful gynaecomastia (enlargement of man’s breasts)

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12
Q

Describe the uses and mechanism of aldosterone antagonists

A
  • Eg. Spironolactone
  • Used to treat heart failure, ascites, hypertension, hyperadrenalism
  • Inhibits aldosterone effect, thus inhibiting Na retention
    • Aldosterone increases expression of ENaC and Na/K ATPase in principal cells of collecting duct
  • Decreases K secretion leading to hyperkalaemia
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13
Q

Describe the uses of ADH antagonists

A
  • Eg. Lithium, tolvaptan
  • Used to treat hyponatraemia and prevent cyst enlargement in polycystic kidney disease
  • Acts as a diuretic, however not a natriuretic
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14
Q

List the ADRs of ADH antagonists

A

Hypernatraemia, deranged liver function

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15
Q

What are general ADR of diuretics

A
  • Anaphylaxis, photosensitivity rash
  • Hypovolaemia and hypotension
    • Activates RAAS and can lead to acute kidney injury
  • Electrolyte disturbance (Na, K, Mg, Ca)
  • Metabolic abnormalities
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16
Q

List common drug drug interactions involving diuretics

A
  • ACE inhibitors and K-sparing diuretics - increased hyperkalaemia leading to cardiac problems
  • Aminoglycosides and loop diuretics - ototoxicity and nephrotoxicity
  • Digoxin and thiazide/loop diuretics - hypokalaemia increases digoxin binding and toxicity (digoxin more toxic with low K)
  • ß-blockers and thiazides - hyperglycaemia, hyperlipidaemia, hyperuricaemia
  • Steroids and thiazide/loop diuretics - increased risk of hypokalaemia
  • Lithium and thiazide/loop diuretics - lithium toxicity (thiazides), reduced lithium levels (loop)
  • Carbamazepine and thiazide - increased risk of hyponatraemia
17
Q

List the drugs used to treat hypertension

A
  • Thiazide diuretics - vasodilation as well as diuresis
  • Spironolactone - especially hyperaldosteronism
  • (ACE inhibitors / Ang II antagonists)
  • (ß-blockers)
18
Q

List the drugs used to treat heart failure

A
  • Loop diuretics - best at removing fluid
  • Spironolactone - non-diuretic benefits (remodeling of heart)
  • (ACE inhibitors / Ang II antagonists)
  • (ß-blockers)
  • May need to increase diuretic dose as drug not delivered to kidney well
19
Q

List the drugs used to treat decompensated liver disease (low albumin, ascites)

A
  • Spironolactone

- Loop diuretics

20
Q

List the drugs used to treat nephrotic syndrome

A
  • Loop diuretic - big doses needed
  • +/- Thiazides
  • +/- Potassium-sparing diuretics/potassium supplements
  • May need to increase diuretic dose as gut swollen in nephrotic syndrome - decreased reabsorption of drug
    • Give IV furosemide IV if gut oedema likely
21
Q

Describe the problems of prescribing diuretics in renal failure

A
  • Patients with CKD have decreased GFR leading to salt and water retention
  • Patients given loop diuretics +/- thiazide
  • Avoid giving K-sparing diuretics - patients with renal failure have reduced potassium secretion leading to hyperkalaemia
  • Not all nephrons working - may need to increase dose of diuretics to achieve desired effect
  • When prescribing gentamicin/vancomycin, careful with dose as nephrotoxins causes nephron dysfunction
22
Q

Describe causes of hyperkalaemia

A
  • Excess intake
  • Movement out of cells - acidosis, hypertonicity, tissue (muscle) damage
  • Reduced urine loss - reduced GFR, reduced distal delivery of Na, reduced secretion in collecting duct
  • Drugs - RAAS inhibitors, NSAIDs, ENaC blockers
23
Q

Explain the effect of hyperkalaemia on the heart

A
  • Increase in potassium levels increases the resting membrane potential closer to threshold
  • At first, this increases the excitability of the heart
  • At higher concentrations, this leads to a decrease in excitability of the heart due to inactivation of sodium gated channels
24
Q

Explain the effect of hypokalaemia on the heart

A
  • In hypokalaemia, the increase in gradient between IC and EC potassium levels leads to hyperpolarisation and therefore shifting resting potential further from threshold
  • However in SA and AV node, hyperpolarisation enhances the funny current and thus depolarisation frequency
    • Leads to increased excitability and possible ventricular fibrillation and arrhythmias
25
Q

Describe the management of hyperkalaemia

A
  • Identify cause
  • ECG
  • Treatment
    • Protect the heart from toxicity - calcium gluconate
    • Lower serum K - insulin/dextrose, remove K from diet
      • Remove K from body - calcium resonium

4 - CPT (23 decks)

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