Spironolactone and Eplerenone: A Cardiologist's Guide to Two Quietly Powerful Blood Pressure Medications

Spironolactone and eplerenone are close cousins, so I treat them as one decision in clinic and only split them apart when a specific reason comes up. In my Encinitas practice, these are the pills I reach for when someone is already taking two or three blood pressure medications and the numbers still sit too high. They are not new, they are not expensive, and they are quietly two of the most useful tools I have. This guide walks through how they work, why they are so good for stubborn high blood pressure, the one side effect that deserves real respect, and the surprising bonus effects on hair and skin.

What Are Spironolactone and Eplerenone?

Spironolactone and eplerenone are aldosterone blockers. Aldosterone is a hormone that tells your kidneys to hold onto salt and water, which raises blood pressure. These pills block that signal, so your body releases the extra salt and water and your blood vessels relax. Doctors group them under the name mineralocorticoid receptor antagonists, or MRAs.

Think of aldosterone as a thermostat that got stuck on “hold onto salt.” The more salt and water your body keeps, the more fluid sits inside your blood vessels, and the harder your heart has to push. Blocking aldosterone turns that thermostat back down. You let go of the surplus salt and water through your urine, the volume inside your vessels drops, and the pressure eases. The medication does this work in the kidney, at the spot where your body decides how much salt to keep and how much potassium to throw away.

Spironolactone came first, back in the 1960s. Eplerenone arrived decades later and was designed to do the same core job with a cleaner aim. Spironolactone blocks aldosterone, and it also bumps into the receptors for male-type hormones and progesterone. Eplerenone was built to aim almost entirely at the aldosterone receptor and leave those hormone receptors alone. Both lower blood pressure well. The differences between them come down to side effects, which I will get to, because that is usually what decides which one a given person ends up taking.

One practical tip on spironolactone: take it with food. Eating roughly doubles how much of the drug your body absorbs, so a consistent habit of taking it with a meal keeps the effect steady.

Why I Reach for Them When Blood Pressure Won’t Budge

For high blood pressure that resists the usual medications, an aldosterone blocker is the single best add-on pill we have good evidence for. National guidelines and recent reviews of resistant high blood pressure name spironolactone as the preferred fourth medication to add.

Most people get to goal on one or two medications. Some do not. When blood pressure stays high despite three medications taken correctly, including a water pill, we call that resistant high blood pressure. For years we argued about the best fourth pill to add. The evidence now points clearly to aldosterone blockers. A 2026 review in JAMA on resistant high blood pressure, along with the American College of Cardiology and American Heart Association guidelines, puts spironolactone first among the options for the fourth drug, because it lowers pressure more than the alternatives in exactly the people who have run out of other choices.

That result lines up with what I see in clinic. When someone has been frustrated for months, watching their readings stay high on a fistful of pills, adding a low dose of spironolactone or eplerenone often does what nothing else has. Eplerenone is a reasonable choice here too. It is somewhat less potent, lowering the top blood pressure number by around 9 points compared with placebo, so I tend to dose it higher or twice a day to match the effect.

The Hidden Reason Some Blood Pressure Stays High

A lot of stubborn high blood pressure is driven by too much aldosterone in the first place. Sometimes that comes from a small, benign overactivity in the adrenal glands, the little hormone factories that sit on top of the kidneys. We call that condition primary aldosteronism, and it is more common than people think. When aldosterone is the problem, a medication that blocks aldosterone is the obvious fix, which is part of why these pills work so well in people who have run out of other options. If your blood pressure has been hard to control, it is worth asking me whether a simple blood test for aldosterone makes sense for you. You can read more in my piece on secondary causes of high blood pressure.

A Quiet Second Job: Protecting a Weak Heart

Beyond blood pressure, these medications help people with a weakened heart muscle live longer. They are one of the four pillars of treatment for heart failure with reduced ejection fraction, which means the main pumping chamber has become weak.

This is a secondary use, but it matters, so I want to mention it. When the heart muscle weakens and cannot pump as forcefully as it should, four groups of medications have each been shown to help people live longer and stay out of the hospital. Cardiologists call them the four pillars. Aldosterone blockers are one of those four pillars, alongside a class that relaxes blood vessels and protects the kidneys, beta blockers, and the newer SGLT2 inhibitors. The 2022 American Heart Association and American College of Cardiology heart failure guideline recommends one of these aldosterone blockers for the right patients, as long as kidney function and potassium are acceptable.

The evidence here is strong and decades deep. Spironolactone earned its place in severe heart failure by cutting the risk of death by about a third, which is why the FDA approves it to improve survival in people with weakened hearts. For eplerenone, two large trials sealed the case. The EMPHASIS-HF trial, in people with milder heart failure symptoms, lowered the combined risk of dying or being hospitalized by 37 percent. The EPHESUS trial, in people whose hearts were weakened after a heart attack, reduced the risk of death by 15 percent. So when I prescribe one of these for a patient with a weak heart, I am leaning on some of the best-tested medicine we have. The 2022 guideline treats spironolactone and eplerenone as equally effective here, so the choice usually comes down to side effects.

The One Side Effect I Watch Closely: Potassium

These medications can raise the potassium level in your blood. High potassium usually causes no symptoms at all, so the only way to catch it is a blood test. The FDA label advises checking potassium and kidney function within the first week of starting, again after any dose increase, then on a regular schedule. I follow that closely.

I want to be straight with you about this without making it sound frightening. Aldosterone normally helps your body get rid of potassium. When we block aldosterone, your body holds onto a little more of it. For most people that shift is small and harmless. In some people, especially those with reduced kidney function or those taking certain other heart and blood pressure medications, potassium can climb higher than we want. This risk is similar for both spironolactone and eplerenone.

Here is the part that deserves your attention. A rising potassium level is silent. You will not feel tired, you will not feel a warning twinge, you will feel completely normal right up until a blood test shows it. If potassium climbs high enough, it can disturb the heart’s electrical rhythm, and that is the outcome we are working to prevent. The good news is that this is easy to stay ahead of. A simple blood draw catches it early, long before it becomes a problem, and we adjust the dose or the plan from there.

So the deal I make with my patients is this. The pill is excellent, the monitoring is simple, and the two go together. Do not skip the early lab check. That one blood test is what turns a powerful medication into a safe one. A few practical habits help too. Go easy on salt substitutes, since most of them are made of potassium. Tell me about any new medication or supplement before you add it, including over-the-counter potassium and the common blood pressure pills that act on the same hormone system. And if you ever feel unusual muscle weakness or a fluttering heartbeat, let me know promptly.

Spironolactone or Eplerenone: Which One and Why

Both lower blood pressure well. The choice usually comes down to side effects. Spironolactone is stronger milligram for milligram and gives the bonus hair and skin effects, but it can cause breast tenderness in men. Eplerenone is cleaner and rarely causes that, so I usually choose it for my male patients.

Spironolactone’s extra reach into the male-hormone and progesterone receptors is the source of both its bonus effects and its main nuisance. In men, blocking those androgen receptors can cause breast tenderness or some breast swelling. In studies, this shows up in roughly 8 percent of men on spironolactone, and the risk climbs at higher doses. It is not dangerous, but it is uncomfortable and understandably bothersome, and it usually reverses once we stop or switch the medication.

Eplerenone is the selective one, so it leaves those hormone receptors alone. The payoff is that breast tenderness is rare, reported in well under 1 percent of patients. That is why, for a man who needs an aldosterone blocker, eplerenone is usually my first pick. He gets very similar blood pressure control without the breast tenderness risk.

The trade-off is modest. Eplerenone is about half as potent as spironolactone milligram for milligram, and it clears the body faster, so I dose it higher or split it into a morning and evening dose. Pushed to the right dose, it controls blood pressure about as well. It also tends to cost more, since spironolactone has been generic for ages, and it interacts with a few medications that spironolactone does not, so I check your other prescriptions before starting it. There is one more point worth knowing. Some recent studies in heart failure patients have hinted that eplerenone may carry a lower risk of death than spironolactone, though that evidence is observational and not yet proven in a head-to-head trial. I would not switch a patient who is doing well on spironolactone based on that alone, but it is part of why I lean toward eplerenone when I am choosing fresh.

The Surprise Bonus: Thicker Hair and Clearer Skin

Because spironolactone also blocks male-type hormones, some patients notice a welcome side effect: thicker scalp hair and clearer skin. Dermatologists prescribe it off-label for these exact reasons.

This is one of the few times I get to tell a patient that a side effect might be good news. The same androgen-blocking action that causes breast tenderness in men does something different elsewhere in the body. Male-type hormones drive several common skin and hair complaints. They shrink scalp hair follicles in female-pattern hair thinning, they crank up oil glands and feed hormonal acne, and they push unwanted hair growth on the face and body. By turning that signal down, spironolactone can help with all three.

Dermatologists have used spironolactone off-label for years for female-pattern hair loss, hormonal acne, excess facial or body hair, and a stubborn skin condition called hidradenitis suppurativa. These uses are mostly in women, often at higher doses than I use for blood pressure. A patient who comes to me for blood pressure and happens to also have thinning hair or breakout-prone skin may notice both improve. It takes patience, since hair and skin changes unfold over months rather than weeks, but the effect is real and well documented.

Two honest caveats. First, this bonus belongs to spironolactone, not eplerenone, because eplerenone is the selective one that leaves those hormone receptors alone. Second, the same hormonal action is the reason spironolactone is avoided in pregnancy and is not the right choice for everyone. If the hair and skin benefit appeals to you, that is a good conversation to have with me.

Who Should Be Cautious

These are not the right pills for everyone. The main reasons to avoid them or use extra care are reduced kidney function, an already-high potassium level, and certain medication combinations.

If your kidneys are not filtering well, you hold onto potassium more easily, and an aldosterone blocker adds to that. I do not rule the medication out for kidney patients, but I start lower, monitor more closely, and sometimes decide the risk is not worth it. The same caution applies if your potassium already runs high, or if you take other medications that raise potassium, such as some of the common blood pressure pills that act on the same hormone system. Salt substitutes, which are usually potassium chloride, belong on that list too. You can read more about the minerals that matter for your heart in my article on magnesium, potassium, and CoQ10.

These medications can also nudge other lab values, so I keep an eye on kidney function, electrolytes, uric acid, and blood sugar from time to time. Excessive fluid loss is possible if you become dehydrated, especially when an aldosterone blocker is combined with other blood pressure medications, so I watch volume status too. Pregnancy is a clear reason to avoid spironolactone, again because of its hormone-blocking action. And anyone starting one of these should be the kind of patient who will actually come in for the early blood test, since the monitoring is the safety net.

How I Start and Monitor These Medications

I keep the routine simple, because a simple routine is one people actually follow. I start at a low dose, usually 25 mg of spironolactone or 50 mg of eplerenone. I check potassium and kidney function before starting if I do not already have recent numbers, then again within the first week. If those look good and your blood pressure needs more help, I move the dose up and recheck. After things are stable, periodic labs are enough.

Home readings make a big difference here, because they tell us whether the medication is doing its job in your real life rather than just in my office. If you are not already tracking your numbers at home, my guide to home blood pressure monitoring walks through how to do it accurately. Pairing one of these medications with the basics that lower pressure on their own, like weight loss and exercise and cutting back on salt, often gets people to goal faster and on a lower dose.

Frequently Asked Questions

Is spironolactone or eplerenone better for high blood pressure?

Both work well. Spironolactone is stronger milligram for milligram and is the better-studied of the two for resistant high blood pressure. Eplerenone is gentler on hormone-related side effects, which is why I often choose it for men, though it is about half as potent and may need a higher or twice-daily dose. For most people the decision is about side effects, not effectiveness.

Why do I need a blood test soon after starting?

These medications can raise your potassium, and a high potassium level causes no symptoms. The only way to catch it early is a blood test. The drug label advises checking potassium and kidney function within the first week of starting and after any dose increase. That one habit is what keeps a strong medication safe.

Should I take spironolactone with food?

Yes. Taking spironolactone with food roughly doubles how much your body absorbs, which keeps the effect steady. Pick a meal and take it at the same time each day.

Can spironolactone really help with hair and skin?

Yes, for some people. Because spironolactone blocks male-type hormones, dermatologists use it off-label for female-pattern hair thinning, hormonal acne, and excess hair growth. If you take it for blood pressure, you may notice those improvements as a bonus. The changes take months, not weeks. Eplerenone does not share this effect.

Why does spironolactone cause breast tenderness in men?

Spironolactone blocks male-type hormone receptors along with aldosterone, which in about 8 percent of men can lead to breast tenderness or swelling. It is uncomfortable but not dangerous, and it usually reverses if we stop or switch the medication. Eplerenone rarely causes this, so it is my preferred choice for male patients.

Does spironolactone cause cancer?

This worries people, because the old drug label carries a warning based on very high doses given to animals. In humans, a large 2022 review that pooled many studies found no convincing link between spironolactone and cancer at the doses we actually use. I consider it safe on this front for the patients I treat, and I am happy to talk it through if it concerns you.

Do these medications protect the heart, or just lower blood pressure?

Both. In people with a weakened heart muscle, aldosterone blockers are one of the four medication groups proven to help people live longer and stay out of the hospital. So for the right patient, the same pill that controls blood pressure is also doing protective work.

Can I use a salt substitute while taking one of these?

Be careful. Most salt substitutes are made of potassium chloride, and these medications already nudge your potassium up. Combining the two can push your level too high. Talk to me before using a salt substitute so we can keep an eye on your labs.

References

1. Spironolactone. FDA Drug Label. U.S. Food and Drug Administration. Updated June 3, 2026.

2. Eplerenone (Inspra). FDA Drug Label. U.S. Food and Drug Administration. Updated June 23, 2025.

3. Azizi M, Vongpatanasin W, Fisher NDL, et al. "Diagnosis and Management of Resistant Hypertension." JAMA. 2026.

4. Tam TSC, Wu MH, Masson SC, et al. "Eplerenone for Hypertension." Cochrane Database of Systematic Reviews. 2017.

5. Heidenreich PA, Bozkurt B, Aguilar D, et al. "2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure." Journal of the American College of Cardiology. 2022.

6. Lainscak M, Pelliccia F, Rosano G, et al. "Safety Profile of Mineralocorticoid Receptor Antagonists: Spironolactone and Eplerenone." International Journal of Cardiology. 2015.

7. Elshahat A, Mansour A, Ellabban M, et al. "Comparative Effectiveness and Safety of Eplerenone and Spironolactone in Patients with Heart Failure: A Systematic Review and Meta-Analysis." BMC Cardiovascular Disorders. 2024.

8. Ji K, Huang X, Wang F, et al. "Comparative Safety Profiles of Spironolactone, Eplerenone, and Finerenone: A Pharmacovigilance Study Based on FAERS Data from 2004 to 2024." Frontiers in Pharmacology. 2025.

9. Bommareddy K, Hamade H, Lopez-Olivo MA, et al. "Association of Spironolactone Use with Risk of Cancer: A Systematic Review and Meta-analysis." JAMA Dermatology. 2022.

10. Harrington JL, Canonico ME, El Rafei A, et al. "Nonsteroidal and Steroidal Mineralocorticoid Antagonists: Rationale, Evidence, and Unanswered Questions." JACC: Heart Failure. 2025.

11. Pardo-Martínez P, Barge-Caballero E, Bouzas-Mosquera A, et al. "Real World Comparison of Spironolactone and Eplerenone in Patients with Heart Failure." European Journal of Internal Medicine. 2022.

12. Adler GK, Stowasser M, Correa RR, et al. "Primary Aldosteronism: An Endocrine Society Clinical Practice Guideline." Journal of Clinical Endocrinology & Metabolism. 2025.

Published on damianrasch.com. The above information was composed by Dr. Damian Rasch, drawing on individual insight and bolstered by digital research and writing assistance. The information is for educational purposes only and does not constitute medical advice.