Spironolactone is a prescription medicine that belongs to the mineralocorticoid receptor antagonist (MRA) drug class, often called a “water pill” because it can increase salt and water loss through the kidneys. It also works as an anti-androgen, which can reduce the effects of certain hormones.
What is spironolactone used for?
It’s commonly prescribed for conditions where reducing salt/water retention or blocking hormone effects is helpful, including:
- Fluid retention and swelling (edema) from heart-related or other causes
- High blood pressure
- Low potassium levels or conditions involving hormones that affect potassium balance
- Hormone-related conditions such as acne or excess facial/body hair due to androgen activity (off-label in some uses)
Is spironolactone a blood pressure medication or a diuretic?
Yes. Spironolactone lowers blood pressure partly by reducing fluid volume and salt retention. It also acts like a diuretic, but it’s considered a “potassium-sparing” diuretic, meaning it can raise potassium levels rather than lower them.
How does spironolactone differ from other diuretics?
Many diuretics increase urine output by causing the body to lose potassium. Spironolactone is different because it blocks mineralocorticoid signaling in a way that tends to conserve potassium. That’s one reason it requires attention to potassium levels during treatment.
What side effects do people worry about?
Common concerns include:
- High potassium (hyperkalemia), which can be dangerous in severe cases
- Dizziness or lightheadedness
- Breast tenderness or enlargement, and other hormone-related effects (because of its anti-androgen activity)
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