Diuretics

Question 1

Loop diuretics:
Example
Mechanism of action
Indications
DDIs/ADRs

Answer 1

E.g. Furosemide

Act on NKCC2 transporters in TAL: prevent reabsorption of Na and Cl (and excretion of Ca and Mg)

Heart failure, liver failure

Dont use with aminoglycosides (ototoxicity, nephrotoxicity)
Avoid use with digoxin and steroids (risk hypokalaemia)

Question 2

Thiazides:
Example
Mechanism of action
Indications
DDIs/ADRs

Answer 2

E.g. Benzoflumathiazide?

Act on Na-Cl symporter and promote Ca reabsorption in DCT

Used in heart failure and hypertension
Used to treat kidney stones (calcium reabsorption from urine)

Do not use with digoxin and steroids (risk hypokalaemia)
Do not use with beta blockers (hyperglycaemia, hyperlipidaemia, hyperuricaemia - risk gout)

Question 3

Potassium sparing diuretics:
Example
Mechanism of action
DDIs/ADR

Answer 3

E.g. Amiloride

Act on ENaC in late DCT and CD
No effect on potassium reabsorption

Do mot use with ACEi: risk hyperkalaemia

Question 4

Aldosterone antagonists:
Example
Mechanism of action
Indications
DDIs
ADRs

Answer 4

E.g. Spironolactone

Inhibit action of aldosterone at. Mineralocorticoid receptors
So affecting Na/K/ATPase and ENaC protein synthesis in CD

Used in heart failure, hypertension, liver failure, hyperaldosteronism (e.g. Conn’s syndrome)

No real DDIs

ADRs: hyperkalaemia, some androgenic cross-reactivity (gynaecomastia)

Question 5

What are the 4 main types of diuretic currently used in clinical practice

What are the 3 types of diuretics used less freqently

Give examples

Answer 5

Clinical use:
Loop diuretics (e.g. Furosemide)
Thiazides (e.g. Bonzoflumathiazide)
Potassium sparing diuretics (e.g. Amiloride)
Aldosterone antagonists (e.g. Spironolactone)

Less frequent use:
Carbonic anhydrase inhibitors (in PCT: used in glaucoma)
Osmotic diuretics (in PCT, DL, CD e.g, mannitol: used in cerebral/pulmonary oedema)
ADH antagonists (in CD)