Diuretics

Question 1

what is a diuretic

Answer 1

a substance which causes diuresis

Question 2

what is diuresis

Answer 2

increased urine production by the kidney

Question 3

how do loop diuretics work

Answer 3

they block the NCCK channels

Question 4

where in the nephron do loop diuretics work

Answer 4

in the loop of Henle

Question 5

what happens to the potassium levels when taking loop diuretics

Answer 5

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

Question 6

why is the counter current multiplier effect lost with loop diuretics

Answer 6

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

Question 7

what do thiazides do

Answer 7

block Na-Cl supporter

Question 8

where do thiazides work in the nephron

Answer 8

early DCT

Question 9

how will thiazides affect the potassium levels

Answer 9

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

Question 10

what are osmotic diuretics

Answer 10

drugs which are osmotically active so prevent water movement out of the tubule

Question 11

how do diuretics inhibiting carbonic anhydrase work

Answer 11

by inhibiting carbonic anhydrase, less bicarb is produced

therefore, the Na bicarb co-transporter does not work so less sodium is reabsorbed

Question 12

true or false: carbonic anhydrase inhibitors cause metabolic alkalosis

Answer 12

false - they cause metabolic acidosis

Question 13

how does alcohol cause diuresis

Answer 13

inhibits ADH

Question 14

what are some adverse effects of diuretics

Answer 14

• abnormal potassium
• hypovolaemia
• hyponatraemia
• increase in uric acid

Question 15

where do potassium sparing diuretics work

Answer 15

collecting duct

Question 16

where do osmotic diuretics works

Answer 16

PCT

Question 17

where do carbonic anhydrase inhibitors work

Answer 17

PCT

Question 18

what does amiloride do

Answer 18

inhibits ENaC

Question 19

what effect on potassium does amiloride have

Answer 19

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

Question 20

what does spironolactone do

Answer 20

it is an aldosterone antagonist so prevents the increased expression of ENaC

Question 21

what effect on potassium does spironolactone have

Answer 21

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

Question 22

what is the treatment of Conn’s syndrome

Answer 22

spironolactone

Question 23

what diuretics cause hyperkalamia

Answer 23

potassium sparing drugs

Question 24

what drugs cause hypokalaemia

Answer 24

loop diuretics and thiazides

Question 25

what does aldosterone do

Answer 25

increase ENaC expression

Question 26

why are diuretics required in heart failure

Answer 26

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

Question 27

why are diuretics required in nephrotic syndrome

Answer 27

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

Question 28

why are diuretics used in liver cirrhosis

Answer 28

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