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Spironolactone is a potassium-sparing diuretic (MRA) that blocks the aldosterone receptor. It helps with heart failure and hard-to-control high blood pressure – but requires regular potassium monitoring and can cause breast tenderness in men.
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Never stop spironolactone or change the dose on your own. Especially with heart failure, stopping abruptly can worsen your condition – always discuss changes with your practice and keep an eye on your potassium level. Spironolactone (brand name Aldactone®) is a potassium-sparing diuretic from the group of mineralocorticoid receptor antagonists (MRA). It blocks the action of the hormone aldosterone, thereby producing mild diuresis while protecting the potassium balance. It is used above all for heart failure and hard-to-control high blood pressure.
| Property | Details |
|---|---|
| Active ingredient | Spironolactone |
| Brand name | Aldactone® |
| ATC code | C03DA01 |
| Drug class | Potassium-sparing diuretic – mineralocorticoid receptor antagonist (MRA) |
| Formulation | Tablets/capsules 25, 50, 100 mg |
| Intake | Once daily, preferably in the morning with food |
| Standard dose | 25–50 mg/day (depending on indication) |
| Monitoring | Regular potassium and kidney values required |
| Prescription required | Yes |
| Note | Can cause breast tenderness (gynaecomastia) in men |
The body's own hormone aldosterone makes the kidney retain sodium and water and, in exchange, excrete potassium. Spironolactone occupies the aldosterone receptor and blocks this signal: the body excretes more sodium and water but retains potassium. Hence the name "potassium-sparing" – unlike a loop diuretic such as furosemide, which drives potassium out more strongly.
In heart failure, spironolactone offers an important additional benefit beyond diuresis: it slows the harmful remodelling processes in the heart muscle that a persistently elevated aldosterone level drives. Large studies and the 2023 ESC guideline show that MRAs can prolong life in heart failure. In treatment-resistant high blood pressure – when three blood pressure medicines are not enough – spironolactone is often the most effective next step. It is also used cautiously and under close monitoring in advanced chronic kidney disease.
The dose depends strongly on the area of use. In heart failure the dose is deliberately kept low (usually 25 mg daily) so that potassium does not rise too much. The tablet is best taken in the morning with food, so that the diuretic effect does not disturb your night's sleep.
| Situation | Dose |
|---|---|
| Heart failure | 25 mg once/day (up to 50 mg if needed) |
| Resistant hypertension | 25–50 mg once/day |
| Fluid retention (oedema) | 50–100 mg/day, depending on course |
| Impaired kidney function | Cautious, reduced dose under monitoring |
A missed dose is made up as soon as you notice it – but never take a double amount in one day. What generally applies to a missed dose is explained in the guide Forgotten medication.
brite reliably reminds you of your daily spironolactone intake and documents it seamlessly.
Spironolactone is often compared with two other diuretics. Eplerenone is a related MRA with fewer hormonal side effects; furosemide, by contrast, is a strong, fast-acting loop diuretic that drives potassium out instead of sparing it – the two are frequently combined in heart failure.
| Property | Spironolactone | Eplerenone | Furosemide |
|---|---|---|---|
| Mechanism | MRA (potassium-sparing) | MRA (potassium-sparing) | Loop diuretic |
| Effect on potassium | Retains potassium | Retains potassium | Drives potassium out |
| Diuresis | Mild | Mild | Strong, fast |
| Gynaecomastia | Possible | Very rare | No |
| Typical use | Heart failure, resistant hypertension | Heart failure (with breast tenderness) | Acute fluid retention, oedema |
Which medicine is right depends on your potassium level, kidney function and tolerability. If hormonal side effects occur under spironolactone, eplerenone is often the better alternative. The choice is always made by the doctor.
The most important and potentially most dangerous side effect is a potassium level that is too high (hyperkalaemia). Because spironolactone retains potassium, the level can rise dangerously – especially with impaired kidney function or in certain combinations – and disturb the heart rhythm. That is why regular blood monitoring is mandatory.
| Side effect | Frequency | What to do? |
|---|---|---|
| Raised potassium (hyperkalaemia) | Occasional to common | Monitor regularly; see a doctor if symptoms occur |
| Breast tenderness/enlargement in men (gynaecomastia) | Common (dose-dependent) | Raise it; switch to eplerenone if needed |
| Cycle disturbances, breast tenderness in women | Occasional | Discuss with a doctor |
| Dizziness, low blood pressure | Occasional | Stand up slowly; have the dose checked |
| Worsening of kidney function | Occasional | Monitor kidney values |
What matters most is anything that additionally raises the potassium level. Check combinations in the interaction check.
| Substance / medicine | Interaction | Recommendation |
|---|---|---|
| ACE inhibitors (ramipril) / sartans | Potassium rises markedly | Only with regular potassium monitoring |
| Other potassium-sparing agents, potassium supplements | High risk of hyperkalaemia | Usually avoid |
| NSAIDs (ibuprofen, diclofenac) | Potassium rises, effect falls, kidney strained | Avoid; clarify with a doctor |
| Digoxin | Level may rise | Monitoring needed |
Spironolactone acts not only on the aldosterone receptor but also intervenes slightly in the hormone balance. In men this can lead to tenderness or enlargement of the breast (gynaecomastia), sometimes also to sensitivity of the nipples. This is unpleasant but not dangerous and usually depends on the dose. After stopping, it generally recedes.
Because the same hormonal effect can be used for acne and excessive hair growth, spironolactone is occasionally used specifically for this in women. Important: raise breast tenderness openly at your practice – a lower dose or a switch to eplerenone often provides a good solution. No reason to stop the medicine on your own out of embarrassment.
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