KIDNEY DRUGS Flashcards
diuretic definition
substances that increase the rate of urine production
brief way most diuretics work
increase the concentration of osmotically active agents n the urine, such as sodium or chloride ions
two main types of diuretics + definition
osmotic diuretics- compounds filtered by the kidney which raise osmotic pressure of the urine, drawing water into them
natriuretics- increase the amount of sodium in the urine
example of osmotic diuretic
mannitol
how does mannitol work?
- injected intravenously
- freely filtered by kidney
- raises osmolarity of filtrate, more water moves in
main use of mannitol
treats life threatening oedema, particular cerebral
examples of natriuretics
thiazide diuretics and loop diuretics
when are loop diuretics used?
treatment of heart failure and hypertension
correct electrolyte disturbances, particularly hypercalcaemia
most common example of a loop diuretic
furosemide
action of furosemide
- inhibits the NK2CC transporter in the thick ascending loop of Henle
- less sodium and other ions able to be reabsorbed (remain in the lumen increasing osmolarity)
- raised concentration detected by juxtaglomerular apparatus- triggers renin angiotensin mechanism- afferent arteriole dilates and efferent constricts
- also due to increased ion concentration in lumen, more water moves in in the collecting duct
- also as more ions remain in the lumen, less in the interstitium to pull water out of descending loop
adverse affects of furosemide
hypokalaemia and loss of volume
explain hypokalaemia
NK2CC channel blocked, so less potassium is moving from the lumen to the interstitium
- increased sodium in distal tubule increases sodium movement through the basal sodium potassium pump
- more sodium is being moved into the interstitium whereas potassium is being moved into the cell and then diffuses into the lumen
- also more sodium in distal tubule activates JGA, leads to release of aldosterone
- aldosterone increases sodium potassium ATPase, more potassium loss
explain volume depletion
diuretics produce large amounts of urine, leading to a decrease in blood volume
when are thiazides used?
treat heart failure and hypertension
key example of thiazides
bendroflumethiazide
mechanism of action of bendroflumethiazide
- inhibits the action of NCC in distal convoluted tubule on apical surface of the epithelial cells
- more sodium remains in the lumen, more water remains in the lumen
comparison of thiazides with loop diuretics
less potent
smaller loss of potassium as does not interfere with NA/K pump
two other types of diuretics
potassium sparing and carbonic anhydrase inhibition
2 examples of potassium sparing diuretic
spironolactone and amiloride
action of spiro
competitive antagonist of aldosterone
prevents more ENaC channels and sodium potassium ATPases forming in the collecting duct
less ions reabsorbed, less potassium moved in
action of amiloride
inhibitor of the epithelial sodium channel in the collecting duct
inhibits sodium reabsorption and thus promotes water loss
example of a carbonic anhydrase inhibitor
acetazolamide
acetazolamide mechanism of action
acts in the proximal tubule
- inhibits carbonic anhydrase
- prevents the formation of carbonic acid and thus water and carbon dioxide
- cannot diffuse into the epithelial cell, thus bicarbonate ions remain trapped in the lumen
- increases excretion of bicarbonate ions alongside water, thus diuresis
