Potassium sparing diuretic (Spironolactone) - aldosterone antagonist

Question 1

What are the indications of spirinolactone?

Answer 1

1) Ascites / oedema due to liver failure.
2) Chronic heart failure that occurs 1 month after an MI. (spironolactone given in addition to beta blocker and ACE inhibitor / angiotensin receptor blocker)
3) Primary hyperaldosteronism

Question 2

What is the mechanism of action of spironolactone?

Answer 2

Spironolactone is an ALDOSTERONE ANTAGONIST.

Normally aldosterone produced by adrenal cortex acts on distal tubules to increase the activity of the sodium channels. This allows sodium to move from the lumen into the epithelial cells. Water follows via osmosis. Leading to fluid retention.

Spironolactone works by competitively binding to aldosterone receptors in distal tubule. This stops sodium channels from working. So sodium and water remains in the lumen and are excreted. Potassium is retained.

Question 3

What are the adverse effects of spironolactone?

Answer 3

1) Hyperkalaemia
2) Gynaecomastia + impotence
3) Liver impairment + Jaundice
4) Steven-Johnsosn syndrome (bullous skin eruption)

Question 4

what are the complications of hyperkalaemia?

Answer 4

Muscle weakness
arrhythmias
cardiac arrest

Question 5

What conditions should spirinolactone not be used in?

Answer 5

1) Severe renal failure
2) hyperkalaemia
3) Addison’s disease (aldosterone deficient)
4) Pregnant / lactating women

Question 6

What are the important interactions of spironolactone?

Answer 6

1) Potassium elevating drugs e.g. ACE inhibitors and angiotensin receptor blockers.
2) do not combine with potassium supplements.

Question 7

What route is spirinolactone given?

Answer 7

oral (with food)

Question 8

How can the efficacy of spirinolactone be measured?

Answer 8

reduction in BP, Ascites, oedema

Question 9

How do we ensure safe use of spironolactone?

Answer 9

Monitor renal function, serum potassium.