Spironolactone
Aldactone is the brand-name spironolactone tablet in 25 mg, 50 mg and 100 mg strengths, used for Hypertension, Heart Failure and fluid retention from liver or kidney disease.
Key points
- Unlike most diuretics, spironolactone is potassium-sparing: it blocks aldosterone so the body keeps potassium rather than flushing it out.
- Hyperkalaemia (high potassium levels) is the main risk: avoid potassium supplements, salt substitutes and potassium-rich foods like bananas while taking it.
- Spironolactone controls high blood pressure, heart failure and fluid retention but does not cure these conditions; the full effect may take about two weeks.
How does Spironolactone work?
Spironolactone works by blocking aldosterone, a hormone that tells the kidneys to hold on to sodium and water while releasing potassium. When aldosterone is blocked, the kidneys pass more sodium and water into the urine, which lowers blood volume and eases the strain on the heart. Because potassium is retained rather than lost, spironolactone behaves differently from most other diuretics in the Heart & Blood Pressure range. This potassium-sparing action is why the main safety concern is hyperkalaemia rather than the low potassium that other diuretics cause.