Eplerenone Side Effects: What to Expect and When to Call Your Doctor

Eplerenone (Inspra) is generally well-tolerated compared to older mineralocorticoid receptor antagonists. One of the main reasons patients are prescribed Eplerenone instead of spironolactone is precisely because it causes fewer side effects. That said, Eplerenone does carry real risks — most notably high potassium levels — that require regular monitoring. Here's what every patient on Eplerenone should know.

The Most Important Side Effect: Hyperkalemia (High Potassium)

Hyperkalemia — elevated potassium levels in the blood — is the most clinically significant side effect of Eplerenone. Because Eplerenone blocks aldosterone's effect on the kidneys, less potassium is excreted in the urine, which causes potassium to build up.

Mild hyperkalemia often has no symptoms, which is why regular blood tests are essential. More severe hyperkalemia can cause:

Muscle weakness or fatigue

Tingling or numbness, particularly in the hands or feet

Nausea or vomiting

Slow or irregular heartbeat (palpitations)

In severe cases: cardiac arrhythmia, which can be life-threatening

Your risk of hyperkalemia is higher if you: have kidney disease, have diabetes, take ACE inhibitors or ARBs (like lisinopril or losartan), take NSAIDs (like ibuprofen), use potassium supplements, or eat high-potassium foods in large quantities.

Your doctor will check your potassium and kidney function before you start Eplerenone, again within the first week, and again at one month. After that, monitoring frequency depends on your stability and risk factors.

Common Side Effects of Eplerenone

Beyond hyperkalemia, the following side effects are reported by a meaningful number of patients:

Dizziness or lightheadedness: Especially when standing up quickly. This is due to Eplerenone's blood pressure-lowering effect.

Hypotension (low blood pressure): Particularly when Eplerenone is combined with other blood pressure medications. Symptoms include lightheadedness, fainting, or feeling weak.

Increased creatinine: A mild rise in serum creatinine (a marker of kidney function) is common when starting Eplerenone and is usually not clinically significant in isolation, but should be monitored.

Fatigue: Some patients report mild tiredness, though this is also common in the underlying conditions Eplerenone is used to treat.

Nausea or stomach upset: Usually mild; taking Eplerenone with food can help.

Rare but Reported: Gynecomastia and Hormonal Effects

One of Eplerenone's key advantages over spironolactone is its much lower rate of hormonal side effects. Gynecomastia (breast enlargement in men) occurred in approximately 0.5% of men in clinical trials of Eplerenone — compared to roughly 9-10% of men on therapeutic doses of spironolactone. Women experience fewer menstrual irregularities and sexual side effects with Eplerenone as well.

That said, if you do notice breast tenderness or swelling while taking Eplerenone, report it to your doctor. It's rare but possible.

When to Call Your Doctor Immediately

Contact your prescriber right away — or go to an emergency room — if you experience:

Sudden muscle weakness or paralysis

Heart palpitations or an irregular heartbeat

Feeling faint or actually fainting

Severe nausea, vomiting, or abdominal pain

Numbness or tingling in your extremities that is new or worsening

Foods and Supplements to Avoid

While taking Eplerenone, be careful about:

Potassium supplements or potassium-containing salt substitutes — these can cause dangerous hyperkalemia

Grapefruit juice — increases Eplerenone blood levels by about 25%, which may increase side effects

NSAIDs (ibuprofen, naproxen, aspirin in high doses) — can worsen kidney function and raise potassium

Eplerenone vs. Spironolactone: Side Effect Comparison

Hyperkalemia risk: Similar for both drugs — both require potassium monitoring

Gynecomastia: ~0.5% with Eplerenone vs. ~9-10% with spironolactone at therapeutic doses

Menstrual irregularities: Rare with Eplerenone; more common with spironolactone

Sexual side effects: Significantly less common with Eplerenone due to its receptor selectivity

For more on Eplerenone's drug interactions — which can affect your side effect risk — see our article on Eplerenone drug interactions. And if you're having trouble finding your prescription, use medfinder to find it in stock near you.