Diuretics Flashcards
What are the types of diuretics?
- Loop
- Thiazide
- K+ Sparing (Aldosterone antagonists)
- Osmotic diuretics
- Carbonic anhydrase inhibitors
Give 2 examples of loop diuretics
- Furosemide
- Butemanide
What is the mechanism of action of loop diuretics?
Inhibits Na/K/2Cl co-transporter in the loop of Henle
Give an example of a thiazide diuretics
Bendoflumethiazide
What is the mechanism of action of thiazide diuretics?
Inhibits Na/Cl co-transporter in DCT
How long do thiazide diuretics take to have effect?
1-2 hours
What is the duration of action of thiazide diuretics?
Up to 24 hours
What are aldosterone antagonists also known as?
Potassium sparing diuretics
Give 2 examples of aldosterone antagonists
- Spironolactone
- Amiloride
What is the mechanism of action of aldosterone antagonists?
Prevent reabsorption of Na in the DCT, thus causing Na and H2O excretion and K retention
Give an example of an osmotic diuretic
Mannitol
What is the mechanism of action of osmotic diuretics?
Causes reabsorption of H2O in the PCT and the descending limb of the loop of Henle, and opposes the action of ADH in the collecting duct
Give an example of a carbonic anhydrase inhibitor
Acetazolamide
What is the mechanism of action of carbonic anhydrase inhibitors?
Block carbonic anhydrase at the PCT, so bicarbonate cannot be reabsorbed and is retained in the PCT with H2O and Na
What are the routes of delivery of diuretics?
- PO
- IV
- Topical
What are the indications for loop diuretics?
- Acute pulmonary oedema and chronic heart failure
- Oliguric renal insufficiency
What are the indications for thiazide/thiazide-like diuretics?
- Hypertension
- Nephrogenic diabetes
What are the indications for potassium-sparing diuretics?
- Hypertension
- Hypokalaemia
- Ascites and oedema secondary to hepatic cirrhosis
What are the indications for osmotic diuretics?
- Cerebral oedema
- Raised intraocular pressure
- Treatment of cystic fibrosis
What are the indications for carbonic anhydrase inhibitors?
Glaucoma
What is the role of loop diuretics in heart failure?
They provide symptomatic improvement but do not reduce mortality in heart failure
Describe the use of diuretics in the elderly?
Should be used with caution, and at the lowest dose possible
Why should diuretics be used with caution in the elderly?
Because they are particularly susceptible to side effects
Can diuretics be used in pregnancy?
Should be avoided due to risk of volume depletion
When should loop diuretics be used with caution?
- Hypovolaemia
- Hypotension
- Prostatic hypertrophy
- History of diabetes or gout