What is spironolactone? A Comprehensive Overview

October 11, 2025 •

3 min read

First approved by the FDA in 1960, spironolactone (brand name Aldactone) is a versatile prescription medication known as a potassium-sparing diuretic. Its ability to treat a range of conditions, from heart failure to hormonal acne, is due to its dual mechanism of action as an aldosterone and androgen blocker.

Quick Summary

Spironolactone is a medication used to treat heart failure, high blood pressure, fluid retention, and hyperaldosteronism by blocking the hormone aldosterone. It also has anti-androgen effects, which allow it to be used for acne and hirsutism. Caution is advised for patients with kidney problems due to the risk of high potassium.

Key Points

Dual Mechanism of Action: Spironolactone blocks aldosterone and androgen receptors, treating cardiovascular and hormonal conditions.
Potassium-Sparing Diuretic: It helps the body eliminate excess fluid while preserving potassium levels.
Primary Cardiovascular Uses: Approved uses include heart failure, high blood pressure, and edema.
Common Off-Label Uses: Often prescribed for hormonal acne, hirsutism, and female pattern hair loss.
Key Side Effect: Hyperkalemia: A significant risk is high potassium levels, especially with kidney problems.
Important Drug Interactions: Combining with potassium supplements, ACE inhibitors, or NSAIDs increases hyperkalemia risk.

What is Spironolactone?

Spironolactone, available under names like Aldactone and CaroSpir, is a prescription medication categorized as a potassium-sparing diuretic and an aldosterone receptor antagonist. It functions as a diuretic, aiding the body in removing excess water and sodium via the kidneys, which helps lower blood pressure and reduce fluid buildup. It retains potassium, an electrolyte often depleted by other diuretics. Additionally, spironolactone has hormonal effects, specifically by blocking androgen receptors.

Mechanism of Action

Spironolactone works by interfering with specific hormonal pathways in the body.

Aldosterone Receptor Antagonism

In the kidneys, spironolactone blocks aldosterone from binding to its receptors. Aldosterone is a hormone that promotes sodium and water reabsorption and potassium excretion. By blocking aldosterone, spironolactone increases the excretion of sodium and water, thus lowering blood volume and pressure, while preventing potassium loss.

Anti-Androgen Effects

Spironolactone also blocks androgen receptors and reduces androgen production. This effect is beneficial in treating conditions driven by excess androgens, such as acne and hirsutism in women.

Uses and Applications

Spironolactone's dual action allows it to treat various medical conditions.

Approved Uses

Heart Failure: Used alongside other therapies for severe heart failure to improve survival and reduce hospitalization risk.
High Blood Pressure (Hypertension): An add-on treatment for blood pressure not controlled by other medications.
Edema: Manages fluid retention from conditions like liver cirrhosis and heart failure.
Primary Hyperaldosteronism: Treats and diagnoses this condition of excessive aldosterone production.
Hypokalemia: Treats low potassium caused by other diuretics.

Off-Label Uses

Acne: Effective for hormonal acne in adult women by reducing sebum production.
Hirsutism: Helps treat excessive hair growth in women due to high androgens.
Female Pattern Hair Loss: Anti-androgen properties may help prevent hair thinning in women.

Side Effects and Precautions

Potential side effects range from common to serious.

Common Side Effects

Dizziness and drowsiness
Nausea, vomiting, diarrhea, stomach pain
Irregular menstrual periods, breast tenderness in women
Gynecomastia in men
Changes in sex drive

Serious Side Effects

Hyperkalemia: High potassium is a major risk, especially with kidney issues, causing muscle weakness or irregular heartbeat.
Hyponatremia: Low sodium can cause confusion or headache.
Kidney Problems: Risk of worsening kidney function, particularly with dehydration.
Liver Toxicity: Rare but possible.
Severe Skin Reactions: Rare serious reactions like Stevens-Johnson syndrome.

Drug Interactions

Spironolactone can interact with other medications.

ACE Inhibitors and ARBs: Increased risk of hyperkalemia when combined.
Potassium Supplements and Salt Substitutes: Avoid to prevent high potassium levels.
NSAIDs: Can reduce spironolactone's effect and increase kidney risk and hyperkalemia.
Other Diuretics: Combining with other potassium-sparing diuretics is generally not advised.
Lithium: Spironolactone can increase lithium levels, potentially causing toxicity.

Spironolactone vs. Other Diuretics

Comparing spironolactone to other diuretics highlights its unique features.


Feature	Spironolactone (Potassium-Sparing Diuretic)	Furosemide (Loop Diuretic)	Hydrochlorothiazide (Thiazide Diuretic)
Mechanism	Blocks aldosterone, increases sodium/water excretion, retains potassium, and has anti-androgen effects.	Potently increases salt and water excretion in the loop of Henle.	Promotes moderate salt and water excretion in the distal tubule.
Effect on Potassium	Conserves potassium, risk of hyperkalemia.	Significantly increases potassium excretion, risk of hypokalemia.	Increases potassium excretion, risk of hypokalemia.
Primary Use	Heart failure, hyperaldosteronism, edema, hormonal conditions.	Severe edema and hypertension.	Mild to moderate hypertension and edema.
Onset of Action	Slower, full effect in days to weeks.	Rapid, powerful diuretic effect.	Intermediate onset.

Conclusion

Spironolactone, acting as both a potassium-sparing diuretic and aldosterone antagonist, is a versatile medication with uses in cardiovascular and hormonal conditions. Its anti-androgen effects make it useful for conditions like hormonal acne in women. However, the risk of hyperkalemia necessitates careful monitoring, especially in patients with kidney issues. Spironolactone should always be used under the guidance of a healthcare professional. For more details, resources like the National Institutes of Health are available.

Frequently Asked Questions

Spironolactone is primarily an aldosterone receptor antagonist and a potassium-sparing diuretic. It promotes the excretion of sodium and water while retaining potassium. It also blocks testosterone receptors.

No, spironolactone is a diuretic that helps remove excess fluid, not a blood thinner which prevents clots.

Effects for edema and blood pressure may be seen in a couple of days to two weeks. Hormonal conditions like acne may take several months for noticeable improvement.

Men can take spironolactone for cardiovascular issues. However, it's generally not used for acne or hair loss in men due to feminizing side effects like breast growth.

Avoid potassium supplements and salt substitutes with potassium. Your doctor may also advise limiting high-potassium foods like bananas and avocados to prevent hyperkalemia.

Common side effects include dizziness, nausea, headaches, and stomach cramps. Women may experience irregular periods or breast tenderness, while men might develop gynecomastia.

Avoid alcohol if taking spironolactone for liver disease. For other conditions, moderate alcohol may be permitted, but it can worsen side effects. Consult your doctor.