What Are They For?
MRAs are one of the "four pillars" of HFrEF (heart with weak contraction) treatment, and are also used for resistant hypertension and certain hormonal conditions. In heart failure specifically, they block a hormone (aldosterone) that contributes to harmful heart remodeling and fluid retention.
How They Help (In Plain Terms)
Aldosterone, left unchecked, promotes scarring and stiffening of heart tissue and causes the body to retain sodium while losing potassium. Blocking this hormone protects against harmful structural changes in the heart over time, independent of its modest diuretic effect.
Common Examples
- Spironolactone (Aldactone)
- Eplerenone (Inspra)
- Finerenone (Kerendia) — a newer, non-steroidal MRA with a somewhat different side-effect profile
Common Side Effects to Know
- Elevated potassium levels — the most important one to monitor, since MRAs work in the opposite direction of some other heart medications on potassium
- Breast tenderness or enlargement in men — more common with older MRAs, less with newer ones; mention this to your doctor if it happens, since alternatives exist
- Dizziness
Practical Tips
- Be cautious with potassium supplements and salt substitutes, since many contain potassium (see Medications & Substances to Avoid)
- Report any new breast tenderness to your doctor
- Regular blood tests for potassium are a genuine safety requirement with this medication, not optional monitoring
What Your Care Team Monitors
Potassium levels closely — especially after starting or changing dose, or if other medications or kidney function change — and kidney function generally.
Common Questions
Why do I need blood tests so often with this medication?
Potassium monitoring is a core safety requirement for MRAs — the interval is more frequent than for some other heart medications for good reason.
Is breast tenderness something to worry about?
It's a known side effect, more common with older MRAs — report it, since switching to a different MRA in this class often resolves it.
Can I eat bananas or oranges (high-potassium foods)?
Normal dietary potassium from food is usually fine, but ask your care team about your specific situation, especially if your labs run on the higher side. (See Heart-Healthy Eating for example lower- and higher-potassium food lists.)
What's the difference between finerenone and the older MRAs?
Finerenone is chemically different (non-steroidal) and tends to cause less breast tenderness, though it's used somewhat differently and is newer to heart failure specifically — your prescriber chose the one that fits your particular situation.