29 - Diuretics Flashcards
What are diuretics
Diminish sodium re-absorption at different sites of the nephron –> Increase Na and H20 loss –> decrease in blood volume
What percent of bloody supply do kidneys receive
25%
How much do the kidneys filtrate a day
120ml/min
180L filtrate a day
What are they classes of diuretic
Carbonic anhydrase inhibitors Loop Thiazide Potassium sparing diuretics - prevents excess K+ excretion Osmotic diuretics
Where do carbonic anhydrase inhibitors act on
Proximal convulated tubule
How do carbonic anhydrase inhibitors work
CA is needed to absorb bicarb so that Na+ can be reabsorbed
Example of CA inhibitor
Acetazolamide
What is acetazolomide used for
Glaucoma
Epilepsy
Mountain Sickness (it can appose the alkalosis with acidosis)
Side effects of CA inhibitors
Metabolic acidosis (contraindicated in chronic kidney disease) Sedation Sulphonamide antibiotics (bone marrow suppression)
Examples of loop diuretics
Frusemide
Bumetanide
Where do loop diuretics act
Thick ascending limb (Na/K/2Cl symporter)
What do loop diuretics act on
Block the Cl- portion of the symporter
What do loop diuretics cause to be excreted
K+ Na+ H2O Ca2+ Mg
Indications of loop diuretics
Hypertension
Heart failure
Volume overload for CKD
Side effects of loop diuretics
Hypokalaemia
Dehydration –> acute renal failure, kidney stones, deafness
Where do thiazide diuretics act on
Distal convulated tubule
What is the mechanism of thiazide diuretics
Inhibits Na and Cl- from urine to tubule
Acts on Na+/Cl- symporter
Examples of thiazide diuretics
Bendroflumethiazide
Hydrochlorothiazide
Thiazide like like drugs
Chlothalidone
Indapamide
Metolazone
How does thiazide diuretics act as a hypertensive
Reduces plasma volume and peripheral resistance
Side effects of thiazide diuretics
Hypokalaemia, hypercalcaemia, hyponatraemia, hyperglycaemia, hypercholesterolaemia
What do potassium sparing diuretics do
Prevent excess K+ excretion
Type of potassium sparing diuretics
Epithelial Na Channel antagonists (ENaC)
Aldosterone antagonists
Examples of ENaC antagonists
Amiloride, Triamterene
Where does ENaC act on and what does it do
Acts on collecting ducts/late DCT
prevents Na into cell from urine
Amiloride uses
Heart Failure
Hypokalaemia
Cirrhosis
Amiloride side effects
Hyperkalaemia
Hyponatraemia
Aldosterone antagonists
Spironolactone
Eperenone
Where do aldosterone antagonist work
Collecting tubule
What do aldosterone antagonists do
Inhibit aldosterone which normally upregulates Na+/K+ on basolateral membrane of intercalated cells
Indications for aldosterone antagonists
Hyperaldosteronism (Conns)
Heart failure
Hypokalaemia
Cirrhosis
SE of aldosterone antagonissts
Hyperkalaemia
Gynecomastia
Hyponatraemia
What are osmotic diuretics
Any osmotically active molecule that is freely filtered in the glomerulus and is not reabsorbed by the tubules
Example of osmotic diuretic
Mannitol IV - fast acting, fast metabolism
What does mannitol do
Increase osmolality in the tubular lumen – stops water absorption
MoA of osmotic diuretics
Reduces re absorption of all solutes (Na, K+,urea, drags Na from interstitium)
Indications of osmotic diuretics
Cerebral oedema
Oliguric acute renal failure
Side effects of osmotic diuretics
Transient fluid overload
Urea (disequilibrium syndrome)
When to not use diuretics
When hypotensive When dehydrated When hypokalaemic (Loop/Thiazide) When hyperkalaemic (Amiloride, aldosterone antagonists) Post surgery, with a poor urine output
