Diuretics Flashcards
what is a diuretic
a substance which causes diuresis
what is diuresis
increased urine production by the kidney
how do loop diuretics work
they block the NCCK channels
where in the nephron do loop diuretics work
in the loop of Henle
what happens to the potassium levels when taking loop diuretics
get hypokalaemia
this is because by blocking Na reabsorption in the loop of henle, there is increased absorption in the principal cells
also there is more water to wash the K away in the lumen giving a greater gradient
why is the counter current multiplier effect lost with loop diuretics
as the descending limb is what creates the salt gradient in the medulla interstitum - so this gradient production is blocked by loop diuretics and so water also does not follow
what do thiazides do
block Na-Cl supporter
where do thiazides work in the nephron
early DCT
how will thiazides affect the potassium levels
get hypokalaemia
this is because by blocking Na reabsorption in the early DCT, there is increased absorption in the principal cells
also there is more water to wash the K away in the lumen giving a greater gradient
what are osmotic diuretics
drugs which are osmotically active so prevent water movement out of the tubule
how do diuretics inhibiting carbonic anhydrase work
by inhibiting carbonic anhydrase, less bicarb is produced
therefore, the Na bicarb co-transporter does not work so less sodium is reabsorbed
true or false: carbonic anhydrase inhibitors cause metabolic alkalosis
false - they cause metabolic acidosis
how does alcohol cause diuresis
inhibits ADH
what are some adverse effects of diuretics
- abnormal potassium
- hypovolaemia
- hyponatraemia
- increase in uric acid
where do potassium sparing diuretics work
collecting duct
where do osmotic diuretics works
PCT
where do carbonic anhydrase inhibitors work
PCT
what does amiloride do
inhibits ENaC
what effect on potassium does amiloride have
hyperkalaemia
as the ENaC is linked with a potassium channel, so with less Na moving in there is less of a gradient for potassium to move out
what does spironolactone do
it is an aldosterone antagonist so prevents the increased expression of ENaC
what effect on potassium does spironolactone have
hyperkalaemia
and there are less ENaC and ENaC are linked with K channels,so with less Na moving in there is less of a gradient for potassium to move out
what is the treatment of Conn’s syndrome
spironolactone
what diuretics cause hyperkalamia
potassium sparing drugs
what drugs cause hypokalaemia
loop diuretics and thiazides
what does aldosterone do
increase ENaC expression
why are diuretics required in heart failure
as the drop in cardiac output, leads to reduced renal perfusion and so RAAS activation
also gives an increase in venous pressure giving oedema
this means diuretics are required to remove the excess fluid causing the oedema and from RAAS activation
why are diuretics required in nephrotic syndrome
there is protein loss in the nephron causing a decrease in oncotic pressure so less fluid is taken back up in the vessels giving oedema
RAAS is then activated by the reduced fluid in circulation
therefore, diuretics prevent salt/water retention from RAAS and remove extra fluid from oedema
why are diuretics used in liver cirrhosis
fibrous bands cause blood obstruction in portal vessels giving increased pressure - forcing fluid out
also less oncotic pressure as less albumin is produced
RAAS activated from the lower circulatory volume - so diuretics needs to combat RAAS effects
