11. Diuretics Flashcards
What is the general role of diuretics?
Act on kidney to increase production of urine and to eliminate water from the body
What can diuretics help to do?
Reduce plasma volume and cardiac output
Reduce blood pressure
Reduce oedema/ascites
What are the 5 main classes of diuretics?
Carbonic anhydrase inhibitors Osmotic diuretics Loop diuretics Potassium sparing diuretics Thiazides and thiazides-like diuretics
Generally, how do diuretics work?
Act by interfering with the normal sodium reabsorption by the renal tubules resulting in Na+ and water excretion
Where in the nephron do carbonic anhydrase inhibitors and osmotic diuretics act?
PCT
Where in the nephron do loop diuretics act?
Thick ascending limb of loop of Henle
Where do thiazide and thiazides like diuretics act in the nephron?
DCT
Where do potassium sparing diuretics act in the nephron?
Late DCT and CD
How do carbonic anhydrase inhibitors work?
Inhibit carbonic anhydrase, less H2O and CO2 are taken up into the cell, therefore less Na+ is reabsorbed from the cells in proximal tubule
Give an example of an osmotic diuretic
Mannitol (IV)
How do osmotic diuretics work?
Mannitol in blood, moves into tubule at kidney, draws water into the tubule, increased water excretion but not much Na+ excreted
What are some problems with osmotic diuretics?
Expands the extracellular fluid volume initially
Decrease blood viscosity
Inhibit renin release, increase renal blood flow
When are osmotic diuretics used?
Acute renal failure due to shock or trauma
Acute drug poisoning
To decrease intracranial and intraocular pressure before ophthalmic or brain procedures
What are some side effects of osmotic diuretics?
Headache, nausea, vomiting due to hyponatremia
Extracellular volume expansion, complicates heart failure and pulmonary oedema
Contraindicated in chronic heart failure
Excessive use leads to dehydration and hypernatraemia
How do loop diuretics work?
Block Na+/K+/2Cl- co transporter
Reduce amount of Na+ reabsorbed
Very fast acting
Give 2 examples of loop diuretics
Bumetanide
Furosemide
When are loop diuretics used?
Severe oedema associated with congestive heart failure, nephrotic syndrome Treatment for oliguric ARF Treatment for hypercalcaemia Acute pulmonary oedema Acute hyperkalaemia Toxicity of Br, F, I
What are the side effects of loop diuretics?
Hypovolemia Hyponatraemia Hypokalaemia Hypomagnesaemia Hypocalcemia Metabolic alkalosis Postural hypotension
How do thiazides and thiazides like diuretics work?
Block Na+/Cl- co transporters, reducing amount of Na+ reabsorbed
First line antihypertensive
What are the effects of thiazides and thiazide like diuretics on electrolyte composition of urine?
Increased urinary NaCl excretion Increased urinary K excretion Increased urinary magnesium excretion Decreased calcium excretion Decreased uric acid excretion
What are thiazides used for?
Essential hypertension Mild heart failure Calcium nephrolithiasis due to hypercalciruria Osteoporosis Nephrogenic diabetes insipidus polyuria
How do potassium sparing and aldosterone antagonist diuretics work?
Block aldosterone receptor, no increase in up regulation of ENaC channels and ROMK channels
Potassium sparing block K+ channels, no 3Na+/2K+ pump
Reduce reabsorption of sodium
Give an example of a potassium sparing diuretic
Amiloride
Give an example of an aldosterone antagonist diuretic
Spironolactone
What are the uses for potassium sparing and aldosterone antagonists?
Secondary hyperaldosteronism
CHF, hepatic cirrhosis, nephrotic syndrome
Treatment of hypertension
When is potassium sparing and aldosterone antagonists contraindicated?
In patients with hyperkalaemia and liver disease
