Diuretics

Question 1

Which diuretic increases calcium excretion?

Answer 1

Frusemide

Question 2

Which diuretic reduces calcium excretion?

Answer 2

Thiazide

Question 3

Acetazolamide

Answer 3

CA inhibitor in PCT. Block CA (norm. allows bicarb reabsorption, with proton excreted in exchange for Na absorption). Weak diuretic - generally just used for glaucoma and severe met. alkalosis. ADE: can cause met acidosis.

Question 4

Canagliflozin, dapagliflozin

Answer 4

SLGT2 inhibitor. Blocks PCT SLGT2 symport (high capacity, low affinity), which absorbs glucose and sodium. Used in diabetes

Question 5

Frusemide

Answer 5

Loop diuretic, act in ALoH on sodium/potassium/2cl symport (driven by basolateral Na/K/ATPase). Normally, ROMK channels allow K leaking in exchange for Ca/Na/Mg paracellularly, so their absorption reduced.
Potent diuretics, used in oedema, chronic renal failure and hypercalcaemia. ADE: hypokalaemia, hyponatraemia, hypomagnesaemia
at high dose, IV, long time can cause tinnitus and deafness

Question 6

Thiazide

Answer 6

Acts on thiazide sensitive NaCl symport in DCT (driven by basolateral Na/K/ATPase.
Weak diuretics but FLT for HT, also used in renal calculi to reduce recurrance. ADE: hyponatramia, hypokalaemia, hypercalcaemia, reduce glucose tolerance

Question 7

Amiloride

Answer 7

Potassium sparing, acts in CD, blocks sodium channel (sodium channel under aldosterone control). Weak diuretic, can be combined with others to prevent hypokalaemia. Mainly used for ascites and HF
ADE: hypoerkalaemia (esp with kidney issues)

Question 8

Spironolactone

Answer 8

Potassium sparing, acts in CD, Aldosterone inhibitor (sodium channel under aldosterone control). Weak diuretic, can be combined with others to prevent hypokalaemia. Mainly used for ascites and HF
ADE: hypoerkalaemia (esp with kidney issues), can cause gynaecomastia

Question 9

Counter balances to diuretics (homeostasis)

Answer 9

RAAS activation (ANG2 increases proximal Na reabsorb), Aldosterone increases distal sodium reabsorb. Distal tubule hypertrophy & increased Na/K/ATPase activity increases reabosorption
These effects occur over 2-3 weeks.

Question 10

Diuretic PK

Answer 10

Highly albumin bound, not filtered so enter kidney by secretion. BUT if albumin in tubule (e.g. nephrotic) then diuretic will bind to albumin in tubule and be inactive.
Therefore, may be less effective in those with nephrotic disorder.

Question 11

Diuretic abuse

Answer 11

Mainly loops, typically see hyponatraemia, hypokalaemia, alkalosis, hypocalcaemia, hypomagnesaemia

Question 12

Tolvaptan

Answer 12

V2 receptor blocker, prevents ADH induced AQP2 in CD. Used in SIADH, but also in ADPKD (reduce fluid cysts by reducing cAMP
ADE: hypernatramia and liver function abnormalities.