Names & Terms You Will Hear
Plain-language meanings for the terms your care team may use.
| Term | Meaning |
|---|---|
| MRA (mineralocorticoid receptor antagonist) | The medical name for an aldosterone blocker. It blocks the receptor that the hormone aldosterone acts on. |
| Aldosterone | A hormone that tells the kidney to hold salt and water and to dump potassium. Too much strains and scars the heart. |
| Spironolactone (Aldactone) | The older, stronger aldosterone blocker. Very effective, but it can cause breast tenderness. |
| Eplerenone (Inspra) | A newer, more selective aldosterone blocker. Less likely to cause breast tenderness. |
| Potassium-sparing | These pills keep potassium in the body instead of flushing it out, unlike most water pills. |
| Hyperkalemia | A potassium level in the blood that is too high. It is the main risk of these pills, so we check it with blood tests. |
| Gynecomastia | Breast tenderness or enlargement in men. It can happen with spironolactone and usually eases if we switch to eplerenone. |
| Guideline-directed medical therapy (GDMT) | The set of proven heart failure medicines used together. An aldosterone blocker is one of the four main pillars. |
What Is MRAs: Spironolactone and Eplerenone?
- These pills block a hormone called aldosterone. Doctors call them mineralocorticoid receptor antagonists, or MRAs.
- Aldosterone tells the kidney to hold onto salt and water and to get rid of potassium.
- Too much aldosterone, over years, raises blood pressure and stiffens and scars the heart.
- By blocking aldosterone, these pills help the body let go of extra salt and water, keep potassium, and protect the heart.
- There are two: spironolactone (the older, stronger one) and eplerenone (newer and more selective).
- They are mild water pills, but their bigger job is protecting the heart, not just removing fluid.
- They are taken as a pill, usually once a day. We check your potassium and kidney function with blood tests.
Spironolactone vs Eplerenone
| Feature | Spironolactone | Eplerenone |
|---|---|---|
| Strength | Older, stronger | More selective |
| Breast tenderness | Can happen | Rare |
| Raises potassium | Yes — needs checks | Yes — needs checks |
| Common use | Heart failure, resistant BP | Heart failure, after a heart attack |
Why It Matters
- In heart failure with a weak pump, an aldosterone blocker is one of the four core medicines that work together to protect the heart.
- In a landmark trial (RALES), spironolactone cut the risk of death by about 30 percent in severe heart failure.
- In milder heart failure, eplerenone also lowered death and hospital stays (the EMPHASIS-HF trial).
- For stubborn high blood pressure that three medicines cannot control, spironolactone is the best next pill (the PATHWAY-2 trial).
- They also treat primary aldosteronism, a common hidden cause of high blood pressure where the body makes too much aldosterone.
- Because they keep potassium in the body, we watch your potassium and kidney numbers closely, especially at the start.
- Your doctor chooses spironolactone or eplerenone based on your condition and your side effects.
Use 1 — Heart Failure With a Weak Pump
- This is where these pills help the most. They are one of the four core heart failure medicines.
- In the RALES trial, spironolactone cut the risk of death by about 30 percent in severe heart failure.
- In milder heart failure, eplerenone also lowered death and hospital stays (EMPHASIS-HF).
- They work together with the other core medicines, not instead of them. See our heart failure guide.
- We check potassium and kidney function soon after starting and after any dose change.
Use 2 — Stubborn (Resistant) High Blood Pressure
- Resistant high blood pressure means three medicines are not enough to control it.
- In the PATHWAY-2 trial, spironolactone was the most effective next pill to add.
- It works well because stubborn high blood pressure is often driven by holding too much salt and water.
- We still look for a hidden cause, such as primary aldosteronism.
- As always, we watch potassium and kidney numbers.
Use 3 — Primary Aldosteronism
- In this condition the adrenal glands make too much aldosterone on their own.
- It is a common, often missed cause of high blood pressure, and it can lower potassium.
- An aldosterone blocker treats it directly by blocking the extra hormone.
- If the problem is a single nodule on one side, surgery may be an option instead.
- Your doctor decides based on special blood tests and imaging.
Treatment Options
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
- We start at a low dose and check your potassium and kidney function within a week or two, then again as needed.
- Take the pill at the same time each day, with or without food.
- Do not add potassium supplements or salt substitutes (which are full of potassium) unless we tell you to.
- Tell us about other medicines. Some blood pressure pills and pain relievers can push potassium higher.
- If you get a stomach bug with vomiting or diarrhea, call us. Dehydration can change your potassium and kidney numbers fast.
- If spironolactone causes breast tenderness, tell us. Switching to eplerenone usually fixes it.
- Do not stop the pill on your own. In heart failure it is protecting your heart even when you feel well.
The potassium rule: these pills keep potassium in your body. Too much potassium can harm your heart's rhythm. Do not take potassium supplements or use salt substitutes unless we tell you to, and keep every blood-test appointment. Call us right away for muscle weakness, numbness, or a slow or irregular heartbeat.
Comfort Measures at Home (No Medication Needed)
These simple steps support healing and ease symptoms. Use them alongside any medication your doctor prescribes.
- Follow the low-salt plan we give you. Less salt helps the pill work and eases swelling.
- Know your high-potassium foods (like salt substitutes, oranges, bananas, potatoes) and keep them steady, not piled on.
- Weigh yourself at the same time each day. Report a gain of more than 3 pounds in 2 days.
- Stay hydrated, but do not overdo fluids if we asked you to limit them.
- Keep every lab appointment. The blood tests are how we keep the pill safe.
- Bring a full medicine list, including over-the-counter pills, to each visit.
Risks, Benefits, and Alternatives
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
Every choice has trade-offs. Use this table to start the shared decision conversation with your care team.
| Option | Risks | Benefits | Alternatives |
|---|---|---|---|
| Aldosterone blocker for heart failure (weak pump) | Higher potassium, kidney strain, breast tenderness (spironolactone). Needs blood tests. | One of four core medicines. Cut death about 30 percent in severe heart failure (RALES). | Eplerenone if breast tenderness. Other core heart failure pills, used together. See our HFrEF guide. |
| Spironolactone for resistant high blood pressure | Higher potassium, breast tenderness. Blood tests needed. | The most effective add-on when three pills are not enough (PATHWAY-2). | Other add-on pills, checking for a hidden cause. See our blood pressure guide. |
| Aldosterone blocker for primary aldosteronism | Higher potassium, breast tenderness with spironolactone. | Controls blood pressure and protects organs when the adrenal gland makes too much aldosterone. | Surgery to remove a one-sided adrenal nodule, when suitable. |
| Eplerenone instead of spironolactone | Higher potassium is still possible. Costs more. | Works the same way with far less breast tenderness. A good switch if that side effect appears. | Spironolactone, or finerenone (KERENDIA) for certain kidney and diabetes cases. |
Common Misconceptions
| Myth | Reality |
|---|---|
| A water pill just makes me pee; it cannot be that important. | These are special water pills. Their bigger job is blocking aldosterone to protect the heart. In heart failure, that saves lives. |
| Potassium is good for me, so a pill that keeps potassium must be safe to combine with anything. | Too much potassium is dangerous and can affect the heart's rhythm. That is why we avoid extra potassium and salt substitutes and check your blood. |
| Breast tenderness means something is seriously wrong. | It is a known effect of spironolactone from its hormone action. It is not dangerous, and switching to eplerenone almost always fixes it. |
| I feel fine, so I can skip the blood tests. | High potassium usually has no symptoms until it is dangerous. The blood test is the only way to catch it early. Please keep every appointment. |
| Salt substitutes are a safe way to cut salt on this pill. | Most salt substitutes replace sodium with potassium. On these pills that can push your potassium too high. Ask us before using one. |
| If my blood pressure is normal, I can stop the pill. | In heart failure the pill protects your heart even when your numbers look good. Stopping can let the disease worsen. Talk with us first. |
Possible Complications
Knowing what can go wrong helps you spot problems early. Most complications are uncommon, especially with treatment.
| Where / What | What Can Happen |
|---|---|
| Potassium too high (hyperkalemia) | The main risk. High potassium can cause muscle weakness and a dangerous heart rhythm. We prevent it with blood tests, dose care, and avoiding extra potassium. |
| Kidney strain | These pills can raise kidney numbers, especially with dehydration or other kidney-affecting drugs. We check kidney function along with potassium. |
| Breast tenderness or enlargement | Spironolactone can cause tender or enlarged breast tissue, in men and women, from its hormone action. It is not dangerous. Eplerenone rarely does this. |
| Low blood pressure | Blood pressure can drop, causing lightheadedness when you stand. Stand up slowly and tell us if it is bothersome. |
| Menstrual changes | Spironolactone can cause irregular periods in some women, again from its hormone action. Tell us and we can adjust or switch. |
| Dehydration effects | A stomach bug or too little fluid can quickly change potassium and kidney numbers. Call us early if you cannot keep fluids down. |
Points to Know
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
If you remember nothing else, remember these key points.
- These pills block aldosterone, a hormone that strains and scars the heart.
- In heart failure with a weak pump, they are a core medicine that saves lives.
- For stubborn high blood pressure, spironolactone is the best add-on when three pills are not enough.
- The main risk is high potassium, so we check your blood tests.
- Do not use potassium supplements or salt substitutes unless we say so.
- Spironolactone can cause breast tenderness; eplerenone usually does not.
- Call us if you get vomiting or diarrhea, which can change potassium fast.
- Do not stop the pill on your own.
When to Call Us — and When to Call 911
Shown in English for your safety — this section is not automatically translated. Confirm with your doctor or call the office.
If you are not sure, call. We would rather hear from you twice than miss a real problem.
- Muscle weakness, a slow or irregular heartbeat, numbness, or tingling — these can be high potassium; call us today.
- Vomiting or diarrhea that lasts more than a day — call us; you may need a blood test or a dose hold.
- You are urinating much less than usual — call us this week.
- Breast tenderness or swelling on spironolactone — call us; we can switch you to eplerenone.
- Dizziness or fainting from low blood pressure — call us today.
- You started a new medicine, including over-the-counter pain relievers — check with us; some raise potassium.
- Fainting that you do not recover from quickly, or a collapse — call 911.
Office: (727) 943-5200
Trusted Resources
Independent, evidence-based pages we recommend for deeper reading.
- MedlinePlus — Spironolactone — NIH/NLM patient instructions for spironolactone, including potassium warnings.
- MedlinePlus — Eplerenone — Patient instructions for the more selective aldosterone blocker.
- American Heart Association — Medications Used to Treat Heart Failure — Where aldosterone blockers fit among the core heart failure medicines.
- Our Heart Failure (Weak Pump) Guide — How aldosterone blockers work with the other proven heart failure medicines.
- Our High Blood Pressure Guide — Where spironolactone fits for stubborn high blood pressure.
- Our Diuretics (Water Pills) Guide — How these differ from the potassium-losing water pills.
- Our KERENDIA (Finerenone) Guide — A newer, related medicine for kidney disease with diabetes.
- Our ACE Inhibitors and ARBs Guide — A core partner medicine; combining them makes potassium checks even more important.
Sources Used to Build This Guide
- MedlinePlus — Spironolactone [clinical] — NIH/NLM patient instructions for spironolactone, including potassium and breast-tissue side effects.
- MedlinePlus — Eplerenone [clinical] — Patient instructions for eplerenone, the more selective aldosterone blocker with less breast enlargement.
- American Heart Association — Medications Used to Treat Heart Failure [clinical] — Places mineralocorticoid receptor antagonists among the core heart failure medicines (GDMT).
- NHLBI — Heart Failure [clinical] — Heart failure background for the main use of these medicines.
- MedlinePlus — Heart Failure [clinical] — Condition context and self-care for patients on an aldosterone blocker.
- RALES — Pitt et al., Spironolactone on morbidity and mortality in severe heart failure (NEJM 1999) [trial] — Landmark trial: spironolactone cut the risk of death about 30 percent in severe HFrEF; breast tenderness or enlargement in 10 percent of men vs 1 percent on placebo.
- EMPHASIS-HF — Zannad et al., Eplerenone in systolic heart failure with mild symptoms (NEJM 2011) [trial] — Eplerenone lowered death and heart failure hospitalization in mild (NYHA II) HFrEF; documents the higher-potassium signal to monitor.
- PATHWAY-2 — Williams et al., Spironolactone for drug-resistant hypertension (Lancet 2015) [trial] — Showed spironolactone is the most effective add-on drug for resistant high blood pressure.
- MedlinePlus — Blood Pressure Medicines [clinical] — Framing for the resistant-hypertension use of aldosterone blockers.
