diuretics

Question 1

what is furosemide?

Answer 1

loop diuretic

Question 2

what are the indications for furosemide?

Answer 2

1. salt/water overload associated with oedema
2. acute pulmonary oedema
3. CHF (common indication)
4. renal failure
5. liver cirrhosis

Question 3

mechanism of action of loop diuretics (eg. furosemide)

Answer 3

act at thick ascending limb of Loop of Henle to block Na+/K+/2Cl- co-transporter
- decrease Na+, Mg2+ and Ca2+ reabsorption

Question 4

what are the adverse effects of loop diuretics?

Answer 4

1. hypokalaemia
2. hyperuricaemia
3. hypovolaemia (dizziness, weakness, nausea, cramps, hypotension)
4. hearing loss
5. cardiac arrhythmias

Question 5

what is the mechanism of action of thiazides?

Answer 5

act at distal tubule to inhibit Na+/Cl- co-transporter
- enhance reabsorption of Ca2+ via Ca2+ channels (luminal membrane)

Question 6

how do thiazides lead to hypokalaemia?

Answer 6

increased Ca2+ into tubular epithelial cell → more Na+ pumped into cell via Ca2+/Na+ antiporter (basolateral) → upregulate Na+/K+ ATPase pump → more K+ excreted

Question 7

what is the drug to avoid with thiazides?

Answer 7

digoxin
due to digoxin toxicity
- nausea, vomiting, visual disturbances

Question 8

what is spironolactone?

Answer 8

aldosterone antagonist (K+ sparing diuretic)

Question 9

what are the indications for thiazides?

Answer 9

1. mild to moderate hypertension
2. oedema due to mild to moderate CHF (combine with loop diuretics)

Question 10

what are the indications for aldosterone antagonist (spironolactone)?

Answer 10

1. hyperaldosteronism
2. CHF
3. resistant hypertension

Question 11

what is the mechanism of action of aldosterone antagonist?

Answer 11

act at late distal tubule/collecting duct
- competes with aldosterone for mineralocorticoid receptor → inhibits Na+/K+ ATPase pump → decrease K+ excretion → hyperkalaemia
- block new Na+ channels from forming

Question 12

what drug should be avoided with aldosterone antagonist (K+ sparing diuretic)?

Answer 12

RASi → similar effects to K+ sparing diuretics → increase hyperkalaemia

Question 13

what is amiloride?

Answer 13

sodium channel blocker (K+ sparing diuretic)

Question 14

what is the mechanism of action of sodium channel blocker (K+ sparing diuretic)?

Answer 14

block Na+ channels → less Na+ reabsorbed → less K+ secreted into lumen

Question 15

what is mannitol?

Answer 15

osmotic diuretic

Question 16

what are Dapagliflozin and Empagliflozin?

Answer 16

SGLT2 inhibitors

Question 17

indications for SGLT2 inhibitors

Answer 17

1. hypertension
2. diabetes
3. CVD (decreased mortality)

Question 18

what is tolvaptan?

Answer 18

V2 receptor antagonist

vasopressin acts on V2 receptor → anti-diuretic effects
tolvaptan inhibits v2 receptor → promote diuresis