Aldosterone Blockers in CKD: Spironolactone, Eplerenone, or Finerenone?
You may already be taking one of these medicines without knowing exactly what it is for. A new pill was added at a recent visit and you were told to watch your potassium, or perhaps you have been on the same drug for years and never asked why it is there. Spironolactone, eplerenone, and finerenone all belong to one family of medicines called mineralocorticoid receptor antagonists, usually shortened to MRAs. Patients often call them aldosterone blockers because that is exactly what they do: they block the action of a hormone called aldosterone.
The three drugs share a job but differ in important ways, including which conditions each one has proven benefits for and how their side effects compare. This article explains how they work, who typically gets which drug, and the shared safety issue that matters most with all three: potassium. Our guide to reading your labs covers what a potassium number means; this one goes deeper on the medicines that move it.
What Aldosterone Does, and Why Blocking It Helps
Aldosterone is a hormone made by small glands that sit on top of your kidneys, the adrenal glands. Its main jobs are to tell your kidneys to hold onto salt and water and to let potassium leave in the urine. That sounds harmless until you see what happens when aldosterone runs too high: blood pressure climbs, fluid builds up, and over time the hormone drives inflammation and scarring (fibrosis) in the heart and kidneys. A 2025 review in JACC Heart Failure puts it plainly: blocking the mineralocorticoid receptor helps by reducing “the deleterious effects of aldosterone-induced inflammation, fibrosis, and volume retention.”
MRAs work by occupying the mineralocorticoid receptor, the docking site where aldosterone normally acts. When the receptor is blocked, your kidneys hold less salt and water (which lowers blood pressure) and keep more potassium than usual (which is why monitoring matters). In people with chronic kidney disease (CKD), this double effect is a trade-off: the protection for heart and kidneys can be real, but the potassium side needs active management.
Meet the Three Drugs
Spironolactone is the oldest of the three MRAs, approved by the FDA in 1960. It blocks aldosterone’s receptor and also acts as a mild “water pill” (diuretic). Its landmark trial, RALES, enrolled people with severe heart failure and showed that adding spironolactone cut all-cause deaths by about 30% compared with placebo, and reduced hospitalizations for worsening heart failure by roughly one-third. Today it is used in kidney disease patients mainly for heart failure, resistant high blood pressure (blood pressure that stays above goal despite three medicines), edema, and a condition called primary hyperaldosteronism.
Eplerenone, approved in 2002, was designed to be more selective MRA: it blocks the mineralocorticoid receptor with much less interference at other hormone receptors than spironolactone does. Two large heart failure trials define its evidence base.
In EPHESUS, people who had just had a heart attack and were left with weakened pumping plus heart failure had about a 15% lower risk of dying over a mean follow-up of 16 months when eplerenone was added to standard therapy. In EMPHASIS-HF, which enrolled people with milder (New York Heart Association class II) heart failure, the trial was stopped early because eplerenone cut the combined outcome of cardiovascular death or heart failure hospitalization by 37%. It is also approved as an add-on for high blood pressure.
Finerenone, approved in 2021, belongs to a newer branch of the family: it is a nonsteroidal MRA. Its chemical structure is different from the older two, and it binds almost exclusively to the mineralocorticoid receptor, which keeps hormonal side effects uncommon. Two large trials studied people with type 2 diabetes and CKD who were already on an ACE inhibitor or ARB (the kidney-protective blood pressure medicines; see our article on ACE inhibitors and ARBs in CKD for background).
In FIDELIO-DKD, which focused on people with more advanced disease and heavier protein leakage, finerenone reduced the combined outcome of kidney failure, a sustained 40% or greater drop in eGFR (estimated glomerular filtration rate), or kidney-related death by 18% over a median follow-up of 2.6 years. In FIGARO-DKD, a broader population with earlier-stage disease, it reduced the combined outcome of cardiovascular death, heart attack, stroke, or heart failure hospitalization by 13% over 3.4 years.
Steroidal vs Nonsteroidal: What Actually Differs
The practical difference comes down to selectivity. Spironolactone and eplerenone are steroidal MRAs: their chemical structure is related to steroid hormones, so at higher doses they can also touch other hormone receptors. That explains spironolactone’s most common side effect: breast tissue enlargement (gynecomastia) in men, which occurred in about 9% of male participants in the RALES trial at a typical dose; it usually reverses when the drug is stopped or lowered, but can take months to appear and is more likely at higher doses.
Spironolactone can also cause breast tenderness, menstrual changes, reduced sex drive, and erectile difficulties. Eplerenone was built specifically to avoid most of that hormonal interference, which is why it tends to be better tolerated in those respects.
Finerenone’s nonsteroidal design means it targets the mineralocorticoid receptor almost alone, so these endocrine side effects are uncommon. There is a second difference that matters for kidney patients: where each drug has proven its worth. The steroidal MRAs have their strongest evidence in heart failure and blood pressure control. Finerenone’s outcome evidence comes from people with type 2 diabetes and CKD (and, more recently, milder forms of heart failure; see below).
The KDIGO 2024 guideline is explicit about this split: it suggests a nonsteroidal MRA for adults with type 2 diabetes, an eGFR above 25, normal potassium, and persistent albuminuria despite the maximum tolerated dose of an ACE inhibitor or ARB. For steroidal MRAs, the same guideline notes they may be used for heart failure, hyperaldosteronism, or refractory hypertension, but warns they can cause hyperkalemia or a reversible dip in kidney filtration, particularly when GFR is already low.
One honest caveat: large outcome trials of any MRA in people with CKD from causes other than diabetes are still ongoing, so the kidney-protection story for non-diabetic patients is not yet settled. If you do not have diabetes, your care team’s reason for prescribing one of these drugs may be blood pressure or heart failure rather than direct kidney protection, and that is a perfectly good reason to be on it.
Who Gets Which Drug?
In practice, the choice follows the condition being treated:
- Heart failure with reduced pumping (HFrEF): all three have roles; spironolactone and eplerenone are the classic choices for severe or post-heart-attack heart failure, while finerenone has newer data in milder forms. In FINEARTS-HF, a 2024 trial of people with heart failure whose pumping was mildly reduced or preserved (ejection fraction 40% or higher), finerenone lowered the combined rate of worsening heart failure events and cardiovascular death by 16%.
- Resistant high blood pressure: spironolactone is the usual add-on; our article on resistant and secondary hypertension covers why it works so well there.
- Type 2 diabetes with CKD and protein in the urine (albuminuria): finerenone, per KDIGO 2024, typically added on top of an ACE inhibitor or ARB and often an SGLT2 inhibitor as well; our diabetic kidney disease guide explains the bigger picture.
- Primary hyperaldosteronism: spironolactone (or eplerenone) when surgery is not an option.
A 2025 trial called CONFIDENCE adds a useful data point for people on two of these kidney-protective medicines at once: in people with type 2 diabetes and CKD, combining finerenone with the SGLT2 inhibitor empagliflozin reduced protein in the urine more than either medicine alone. The message is that these therapies can stack, but each addition raises the monitoring burden, which brings us to the shared risk.
The Shared Risk: Potassium
All three drugs make your kidneys hold onto more potassium, and the risk climbs when kidney function is lower, when you have diabetes, or when you also take an ACE inhibitor, ARB, NSAID pain reliever, or a salt substitute containing potassium chloride (see our potassium management guide for the full picture). The good news is that this risk is manageable with a simple rhythm of lab checks:
- Before starting: your care team will check potassium and kidney function first. For finerenone, treatment generally should not start if potassium is already above 5.0 mmol/L; eplerenone carries a similar caution in its labeling.
- Early recheck: the spironolactone label calls for a potassium check within one week of starting or dose changes; finerenone’s schedule checks at about four weeks after starting and after any dose change, then periodically (the KDIGO 2024 monitoring algorithm suggests every four months once stable).
- If it runs high: the usual response is to hold or lower the dose rather than abandon the drug. In the finerenone trials, potassium above 5.5 was managed by pausing and restarting at a lower dose once levels fell back; permanent discontinuation for high potassium happened in about 1.7% of patients versus 0.6% on placebo.
You may also notice a small, temporary rise in creatinine (the lab marker of kidney filtration) within the first few weeks of starting finerenone: it typically stabilizes and is reversible, which is why early labs are scheduled rather than assumed. The same pattern can appear with ACE inhibitors and ARBs; our article on high blood pressure and kidney disease explains why these combinations are worth managing carefully rather than avoiding.
IMPORTANT: Never stop or adjust spironolactone, eplerenone, or finerenone on your own, and never add a potassium supplement or salt substitute without checking with your care team first. Bring a complete list of everything you take, including over-the-counter pain relievers and supplements, to every visit so the full picture is visible; our article on targeted therapy for delaying CKD progression puts these medicines in context with the other kidney-protective options.
What to Take Away
- Spironolactone, eplerenone, and finerenone are all MRAs: they block the hormone aldosterone to lower blood pressure and reduce fluid retention, at the cost of holding onto more potassium
- Spironolactone (1960) is the classic choice for severe heart failure and resistant high blood pressure; its most common side effect is gynecomastia in men (about 9% in trials), usually reversible
- Eplerenone (2002) is a more selective steroidal MRA with proven benefit after heart attack and in milder heart failure, but its label restricts use when kidney filtration falls below about 30 mL/min
- Finerenone (2021) is the nonsteroidal MRA: fewer hormonal side effects, and the only one of the three with large trial evidence for slowing kidney disease progression, so far in people with type 2 diabetes
- All three raise potassium; the safety rhythm is a baseline check, an early recheck after starting or dose changes (one week for spironolactone, about four weeks for finerenone), and periodic monitoring thereafter
- A small early creatinine rise can be normal and reversible; coordinate every change with your care team
Questions Worth Asking Your Care Team
- Which of the three aldosterone blockers am I taking, and which condition is it treating in my case?
- Given my kidney function and other medicines, what is my personal risk for high potassium on this drug?
- When should I recheck my potassium after starting or changing the dose, and how often once things are stable?
- Are any of my other medications, including over-the-counter pain relievers, supplements, or salt substitutes, adding to the potassium risk?
- If my potassium runs high, what is our plan: hold the drug, lower the dose, adjust diet, or something else?
- Is a small rise in my creatinine after starting this medicine expected, and when should I call about it?
- Would finerenone make sense for me if I have type 2 diabetes with protein in my urine, or is there another reason to stay on my current drug?
- What symptoms of high potassium should prompt me to call you sooner rather than wait for my next lab draw?
A Note on This Article
This article is educational information only, not medical advice, diagnosis, or treatment, and it doesn’t replace the judgment of your own care team. Which aldosterone blocker makes sense depends on your kidney function, diabetes status, blood pressure, heart condition, full medication list, and lab results. Your nephrologist may customize any recommendation here to match your stage and labs.
Works Cited
- Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024;105(4S):S117–S314.
- Pitt B, Zannad F, Remme WJ, et al., for the Randomized Aldactone Evaluation Study (RALES) Investigators. The Effect of Spironolactone on Morbidity and Mortality in Patients with Severe Heart Failure. N Engl J Med. 1999;341(10):709–717.
- Pitt B, Remme W, Zannad F, et al., for the Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS) Investigators. Eplerenone, a Selective Aldosterone Blocker, in Patients with Left Ventricular Dysfunction after Myocardial Infarction. N Engl J Med. 2003;348(14):1309–1321.
- Zannad F, McMurray JJV, Krum H, et al., for the EMPHASIS-HF Study Group. Eplerenone in Patients with Systolic Heart Failure and Mild Symptoms. N Engl J Med. 2011;364(1):11–21.
- Bakris GL, Agarwal R, Anker SD, et al., for the FIDELIO-DKD Investigators. Effect of Finerenone on Chronic Kidney Disease Outcomes in Type 2 Diabetes. N Engl J Med. 2020;383(23):2219–2229.
- Pitt B, Filippatos G, Agarwal R, et al., for the FIGARO-DKD Investigators. Cardiovascular Events with Finerenone in Kidney Disease and Type 2 Diabetes. N Engl J Med. 2021;385(24):2252–2263.
- Solomon SD, McMurray JJV, Claggett BL, et al., for the FINEARTS-HF Committees and Investigators. Finerenone in Heart Failure with Mildly Reduced or Preserved Ejection Fraction. N Engl J Med. 2024;391(16):1475–1485.
- Agarwal R, Green JB, Heerspink HJL, et al., for the CONFIDENCE Investigators. Finerenone with Empagliflozin in Chronic Kidney Disease and Type 2 Diabetes. N Engl J Med. 2025;393(6):533–543.
- Harrington JL, Canonico ME, El Rafei A, et al. Nonsteroidal and Steroidal Mineralocorticoid Antagonists: Rationale, Evidence, and Unanswered Questions. JACC Heart Fail. 2025;13(10).
- U.S. Food and Drug Administration. FDA approves drug to reduce risk of serious kidney and heart complications in adults with chronic kidney disease associated with type 2 diabetes (Kerendia [finerenone]). July 9, 2021.
- U.S. Food and Drug Administration. ALDACTONE (spironolactone) tablets prescribing information; initial U.S. approval 1960, revised November 2025.
- U.S. Food and Drug Administration. INSPRA (eplerenone) tablets prescribing information; initial U.S. approval 2002, revised June 2025.
