Diuretics & Renal Pharmacology

Question 1

Name 4 uses for diuretics.

Answer 1

• hypertension
• heart failure
• oedema due to liver disease
• nephrotic syndrome

Question 2

What are carbonic anhydrase inhibitors used for?

Answer 2

Diuretics, primarily used in treatment of glaucoma.

Question 3

What is the MOA of carbonic anhydrase inhibitors?

Answer 3

Inhibits MOA of carbonic anhydrase, which is needed for conversion of H20 + CO2 -> HCO3- + H+. Promotes excretion of Na+, K+ and HCO3-, creating a diuresis.

Question 4

Name 2 complications of carbonic anhydrase inhibitors.

Answer 4

• hypokalaemia

- metabolic acidosis

Question 5

What is the MOA of osmotic diuretics?

Answer 5

Expands ECF, which increases blood flow to kidney and washes out corticomedullary gradient. This prevents loop of Henle from concentrating urine and inhibits reabsorption of Na+ and water.

Question 6

State a complication of osmotic diuretics.

Answer 6

Hypernatraemia - due to proportionately higher Na+ caused by diuresis.

Question 7

Name 2 loop diuretics.

Answer 7

Furosemide

Bumetanide

Question 8

What is the MOA of loop diuretics?

Answer 8

Inhibit NKCC2 transporter in ascending limb of loop of Henle - leads to a natiuresis and diuresis.

Question 9

Name some complications of loop diuretics.

Answer 9

• hypokalaemic metabolic acidosis (K+ shifts out of cells due to a low ECF [K+], causes H+ ions to enter cell and create an acidosis)
• hypocalcaemia and hypomagnesia

Question 10

Out of loop, thiazide and K+ sparing diuretics, which can lead to hypokalaemia and which can lead to hyperkalaemia?

Answer 10

Loop and thiazide - hypokalaemia (hypokalaemic metabolic acidosis).
K+ sparing diuretic - risk of hyperkalaemia.

Question 11

What is the MOA of K+ sparing diuretics?

Answer 11

Block ENaC in the DCT, leads to decreased Na+ and water reabsorption and a natiuresis and diuresis.

Question 12

Name a K+ sparing diuretic..

Answer 12

Amiloride

Question 13

What drug class are bendroflumethiazide and indapamide?

Answer 13

Thiazide diuretics.

Question 14

Spironolactone has 2 drug classes, what are these?

Answer 14

K+ sparing diuretic

Aldosterone antagonist

Question 15

What are aldosterone antagonists used for and what is their MOA?

Answer 15

Diuretics

Inhibit aldosterone, which reduces Na+ and water reabsorption.

Question 16

What are ADH antagonists used for and what is their MOA?

Answer 16

Diuretics

Inhibit action of ADH, leads to a diuresis.

Question 17

Name 2 non-pharmacological substances with diuretic action.

Answer 17

Alcohol - inhibits ADH release.

Caffeine - increases GFR and decreases Na+ reabsorption.

Question 18

Name some generic ADRs of diuretics.

Answer 18

• hypovolaemia and hypotension - can activate RAAS or cause AKI
• electrolyte disturbance
• anaphylaxis or photosensitivity rash

Question 19

What is diuretic resistance?

Answer 19

Failure to have any reduction in oedema despite a full dose of diuretics.

Question 20

State 3 causes of diuretic resistance.

Answer 20

• renal failure - reduced delivery of diuretic to tubule
• heart failure - can’t get to site of action due to reduced blood flow
• nephrotic syndrome - reduced proteins therefore diuretic doesn’t have anything to bind to

Question 21

Why should furosemide be given orally for heart failure?

Answer 21

Due to reduced CO it may not reach site of action, this could lead to diuretic resistance.

Question 22

What is refractory oedema?

Answer 22

Peripheral oedema that doesn’t respond to combined dietary Na+ restriction diuretic treatment with a loop diuretic - need to give a bigger dose to overcome this.

Question 23

Name some potentially nephrotoxic drugs.

Answer 23

• aminoglycosides e.g. Gentamicin, vancomycin
• acyclovir
• NSAIDs

Question 24

Name some drugs that shouldn’t be given if there is impaired renal function i.e. Can become toxic.

Answer 24

• ACEi
• diuretics
• NSAIDs
• metformin

Question 25

Why should you not give NSAIDs, ACEi or ARBs to people with renal problems?

Answer 25

• NSAIDs inhibit vasodilation of afferent arteriole
• ACEi/ARBs inhibit vasoconstriction of efferent arteriole
• this can cause patient to develop AKI

Question 26

What is the MOA of trimethoprim?

Answer 26

ENaC blocker

Question 27

What is calcium gluconate used for?

Answer 27

Used to manage hyperkalaemia - doesn’t reduce K+ but stops the heart reacting to it.