Eplerenone is a prescription medication used for two main purposes: improving survival after a heart attack in people with heart failure, and lowering high blood pressure. Sold under the brand name Inspra, it works by blocking a hormone called aldosterone that plays a central role in fluid balance, blood pressure, and heart damage. It belongs to a class of drugs called mineralocorticoid receptor antagonists, or MRAs, and is one of the foundational treatments in modern heart failure care.
The Two Approved Uses
The FDA approves eplerenone for two specific conditions. The first is heart failure with reduced ejection fraction (meaning the heart pumps less than 40% of its blood with each beat) in stable patients who have recently had a heart attack. In this setting, the drug’s purpose is to improve survival, not just relieve symptoms. The second approved use is high blood pressure in adults, where lowering blood pressure reduces the long-term risk of strokes and heart attacks.
In practice, doctors also prescribe eplerenone for heart failure more broadly, even without a recent heart attack. International guidelines from both the American Heart Association and the European Society of Cardiology give MRAs their strongest recommendation (Class IA) for treating heart failure with reduced ejection fraction, without specifying a preference between eplerenone and its older cousin, spironolactone.
How Eplerenone Works
Your adrenal glands produce a hormone called aldosterone, which tells your kidneys to hold onto sodium and water while flushing out potassium. This is useful in small amounts, but when aldosterone levels stay chronically elevated, as they do in heart failure and some forms of hypertension, the extra fluid increases blood volume, raises blood pressure, and forces the heart to work harder. Over time, excess aldosterone also promotes scarring and stiffening of heart tissue.
Eplerenone sits on the receptor that aldosterone normally binds to, blocking the hormone’s effects. With aldosterone blocked, your kidneys release more sodium and water (a mild diuretic effect) while retaining more potassium. The result is lower blood pressure and less strain on the heart. Beyond fluid balance, blocking aldosterone appears to protect the heart muscle itself from the inflammatory and fibrotic damage the hormone causes, which is why the drug improves survival rather than just symptoms.
Evidence That It Works
The strongest evidence for eplerenone comes from a landmark trial called EPHESUS, which enrolled patients with heart failure after a heart attack. Patients who took eplerenone had a significantly lower rate of cardiovascular death or hospitalization: 26.7% compared to 30.0% in the placebo group, a relative risk reduction of 13%. That may sound modest, but in a population this sick, it translates to meaningful lives saved.
A second major trial, EMPHASIS-HF, extended the evidence to patients with milder heart failure symptoms who had not necessarily just had a heart attack. That study was stopped early because the benefit of eplerenone was so clear. Together, these trials are why guidelines now consider MRAs a core part of heart failure treatment alongside other standard medications.
How It Differs From Spironolactone
Spironolactone was the first aldosterone blocker, and it remains widely used. But spironolactone is not very selective. It also binds to receptors for sex hormones like testosterone and progesterone, which leads to side effects that many patients find difficult to tolerate. In clinical trials, about 13.6% of men taking spironolactone experienced breast-related side effects (breast enlargement or breast pain), and roughly 19% of women did.
Eplerenone was designed to be highly selective for the aldosterone receptor, with very little affinity for other hormone receptors. The difference is dramatic: only about 1% of men taking eplerenone reported breast-related side effects, compared to that 13.6% with spironolactone. For women, the rate dropped from about 19% to under 1%. This selectivity is the primary reason a doctor might choose eplerenone over spironolactone, particularly for patients who have already experienced hormonal side effects on the older drug. The tradeoff is cost: eplerenone is typically more expensive.
Side Effects and Potassium Risk
Because eplerenone causes your kidneys to retain potassium instead of excreting it, the most important side effect is high potassium levels (hyperkalemia). Potassium is essential for normal heart rhythm, but too much of it can be dangerous. In clinical trials, patients taking eplerenone had a higher chance of potassium levels rising above the normal range compared to placebo.
This risk is especially relevant if you already have reduced kidney function, diabetes, or are taking other medications that raise potassium, such as ACE inhibitors or ARBs (which are commonly prescribed alongside eplerenone for heart failure). Your doctor will check your potassium and kidney function through blood tests before starting the medication and periodically afterward. If potassium climbs too high, the dose may be reduced or the drug paused.
Beyond potassium, eplerenone is generally well tolerated. It lacks the hormonal side effects that make spironolactone problematic, and most patients do not notice significant day-to-day symptoms from taking it.
Drug Interactions to Know About
Eplerenone is broken down in the liver by an enzyme called CYP3A4, and certain medications that inhibit this enzyme can cause eplerenone to build up to much higher levels in your blood. Strong inhibitors of this enzyme, like the antifungal ketoconazole, can increase eplerenone exposure by more than fivefold. Other common medications that moderately boost eplerenone levels include the antibiotic erythromycin, the blood pressure drug verapamil, and the antifungal fluconazole, each roughly doubling or tripling the drug’s effective dose in your body.
Grapefruit juice has a minimal effect, raising eplerenone levels by only about 25%. On the other side, St. John’s Wort (an herbal supplement sometimes used for mood) slightly decreases eplerenone levels, which could make it less effective. If you’re prescribed eplerenone, your doctor and pharmacist will review your other medications and supplements for these interactions.
What Taking Eplerenone Looks Like
Eplerenone comes as a tablet taken once or twice daily, with or without food. For heart failure, treatment typically starts at a lower dose and is gradually increased over several weeks, with blood tests to monitor potassium along the way. For high blood pressure, it can be used alone or combined with other blood pressure medications. Most people take it long-term, often indefinitely, since the conditions it treats are chronic.
You will not “feel” eplerenone working the way you might feel a pain reliever. Its benefits play out over weeks and months, reducing fluid overload, protecting your heart from further damage, and lowering your statistical risk of serious cardiovascular events. The drug’s value lies in what it prevents rather than what it relieves day to day.