11. Diuretics

Question 1

Name a carbonic anhydrase inhibitor

Answer 1

Acetazolamide

Question 2

Why are carbonic anhydrase inhibitors not as effective as thiazide or loop diuretics?

Answer 2

Reduction in NaCl is mostly made up for in the loop of Henle

Question 3

How do carbonic anhydrase inhibitors work?

Answer 3

Inhibit carbonic anhydrase in the proximal tubule epithelial cells
H+ usually swapped for Na+ but less H+ produced means reduced absorption of Na+

Question 4

What are the uses of carbonic anhydrase inhibitors?

Answer 4

Chronic glaucoma

Prophylaxis of acute mountain sickness by preventing alkalosis

Question 5

Name 2 loop diuretics

Answer 5

Furosemide

Bumetanide

Question 6

How do loop diuretics work?

Answer 6

Inhibit the Na/K/Cl symporter in ascending loop so that none of them are reabsorbed

Question 7

What are the uses of loop diuretics?

Answer 7

Reduce oedema eg. in CCF
Hypercalcaemia as increased Ca secretion
Lower ICP

Question 8

What are the adverse effects of loop diuretics?

Answer 8

Hypokalaemia (Na/K swap in distal tubule)
Acute hypovolaemia (low BP, shock, arrhythmias)
Increased uric acid
Ototoxicity esp with aminoglycosides

Question 9

Name a thiazide diuretic

Answer 9

Chlorothiazide

Question 10

Where do thiazide diuretics work?

Answer 10

Distal convoluted tubule

Question 11

How do thiazide diuretics work?

Answer 11

Bind to Cl- side of Na/Cl cotransporter and inhibits
Increased Na and Cl in tubule
Reduced K as Na/K swap
Increased calcium absorption
Long term may work to reduce peripheral vascular reststance

Question 12

What are the uses of thiazide diuretics?

Answer 12

Long term hypertension
Reduce oedema in CCF
Prevent recurrent kidney stone formation if high calcium in urine

Question 13

What are the adverse effects of thiazide diuretics?

Answer 13

Low K+
Hypovolaemia
High uric acid, calcium and glucose in blood
Hypersensitivity causing bone marrow suppression and dermatitis

Question 14

Where do K+ sparing diuretics work?

Answer 14

DCT and CD

Question 15

Name 3 K+ sparing diuretics?

Answer 15

Spironolactone
Triamterene
Amiloride

Question 16

How does spironolactone work?

Answer 16

Competes for intracellular aldosterone receptors and prevents action of aldosterone
Mediator protein also increases Na/K exchange

Question 17

What is the active form of spironolactone?

Answer 17

Canrenone

Question 18

What are the uses of spironolactone?

Answer 18

Used with a thiazide diuretic in hypertension as it has little efficacy by itself but useful to keep K+
Secondary hyperaldosteronism

Question 19

What are the side effects of spironolactone?

Answer 19

Gynaecomastia/menstrual irregularities

Hyperkalaemia

Question 20

How do amiloride and triamterene work?

Answer 20

Block luminal Na channel

ie. the one not controlled by aldosterone

Question 21

Name 2 osmotically active diuretics

Answer 21

Urea

Manitol

Question 22

How do osmotic diuretics work?

Answer 22

Increase osmolarity of filtrate so more water is pulled into the tubule

Question 23

What are the uses of osmotic diuretics?

Answer 23

Reduced ICP

Acute renal failure in order to maintain the flow of urine