Diuretics

Question 1

Name 5 different types of diuretics with examples

Answer 1

1) LOOP DIURETICS e.g. furosemide, bumetanide
2) THIAZIDE DIURETICS e.g. bendroflumethiazide, indapamide, metalazone
3) POTASSIUM SPARING DIURETICS e.g. Spironalactone, amiloride + triamterene
4) OSMOTIC diuretics e.g. Mannitol
5) CARBONIC ANHYDRASE INHIBITORS e.g. acetazolimide

Question 2

When are loop diuretics used?

Answer 2

• Treatment of acute pulmonary oedema (rapidly absorbed in GI tract)
• Widely used in peripheral oedema (heart failure, ascites)
• Used to treat sever hyperkalaemia
• Effective in patients with diminished renal function

Question 3

How do loop diuretics work?

Answer 3

Blocks the Na/K/2Cl co-transporter - increases the solute load of filtrate, reduces water resorption. Leads to significant loss of Na Cl, but also K and H.

Question 4

What are the side-effects of Loop diuretics?

Answer 4

• Hypokalaemic metabolic alkalosis (K and H secretion)
• hypovolaemia
• Ototoxicity
• allergic reactions

Question 5

When are thiazide diuretics used?

Answer 5

• Increased BP
• Long term treatment of peripheral oedema (heart failure)
• can reduce renal stone formation in patients with idiopathic hypercalciuria (decrease urine calcium conc)

Question 6

How do thiazides work?

Answer 6

• Act on DCT
• Inhibit NaCl transporter, prevent resorption of NaCl and thus water.
• Cause reduced urinary excretion of Ca

Question 7

What are the side-effects of Thiazide diuretics?

Answer 7

• Hypokalaemia and alkalosis - this is because the increased filtrate sodium levels triggers an exchange with K and H, increasing their excretion
• Hyperuricaemia - thiazides compete with the same co-transporter as uric acid in the kidneys. May lead to gout.
• Impaired glucose tolerance
• Increase plasma cholesterol

Question 8

When are potassium sparing diuretics used?

Answer 8

• Usually used to control K wasting from other diuretics and are given in combination
• Spironolactone and eplerenone used in hyperaldosteronism

Question 9

How do K sparing diuretics work?

Answer 9

• Spironolactone and eplerenone are aldosterone antagonists, hence inhibit the Na retaining action of aldosterone
• Amiloride and triamterene block Na channels in the collecting duct.
• They all increase Na excretion and prevent K and H excretion with a mild associated diuresis
• Spiro is slow acting

Question 10

What are the side-effects of K sparing diuretics?

Answer 10

• Hyperkalaemia is common
• Metabolic acidosis can occur
• Anti-androgenic effects seen with spiro (gynaecomastia)
  + GI upset.

Question 11

What are the uses of osmotic diuretics?

Answer 11

• Haemolysis
• Rhabdomyalosis
• Reducing intra-occular and intra-cranial pressure

Question 12

How do osmotic diuretics work?

Answer 12

Manitol is filtered but not reabsorbed, so hold water in the filtrate.
Slightly increases Na loss

Question 13

What are the side-effects of osmotic diuretics?

Answer 13

• Headache
• Nausea
• Vomitting
• Pulmonary Oedema in anuric patients

Question 14

When are carbonic anhydrase inhibitors used?

Answer 14

Not really used as diuretics but have a use in glaucoma to reduce the formation of aqueous humour.
Also used by climbers to increase respiration (body’s attempt to clear acidosis) and hence improve acclimatisation to altitude and reduce risk of mountain sickness.

Question 15

How do carbonic anhydrase inhibitors work?

Answer 15

They act on the proximal tubule to increase excretion of bicarbonate, and consequently Na K and H20.