Spironolactone: everything you need to know

Spironolactone (brand name Aldactone) is a prescription diuretic medication or "water pill." It helps you get rid of excess fluid and sodium but keeps potassium in the body.

Spironolactone works mainly by blocking the activity of aldosterone (aldosterone antagonist). Aldosterone is a hormone made by the adrenal glands (small glands that sit on top of your kidneys) that encourages sodium and fluid retention. By blocking aldosterone, spironolactone helps you excrete water and sodium—this decreases your overall fluid volume. 

Getting rid of excess water and sodium helps improve heart failure, swelling from nephrotic syndrome, and ascites from liver cirrhosis. Also, like other diuretics (e.g., hydrochlorothiazide), increasing water and sodium excretion helps improve high blood pressure (DailyMed, 2018). 

The common "off-label" uses for spironolactone, treating acne and facial hair (hirsutism) in women, have nothing to do with its ability to block aldosterone. Spironolactone also binds to androgen (male hormone) receptors—this decreases sebum (skin oil) production as well as facial hair growth (Layton, 2017).

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Spironolactone is FDA-approved to treat the following conditions (FDA, 2014): 

• Heart failure, especially NYHA Class III-IV

• High blood pressure, especially if other therapies are not working (not first-line treatment)

• Accumulation of fluid in the body from cirrhosis of the liver (ascites) or kidney problems (nephrotic syndrome)

• Primary hyperaldosteronism

• Low potassium levels (hypokalemia)

Heart failure

Heart failure occurs when your heart is no longer able to pump oxygen-rich blood to the rest of the body as well as it should. This causes problems like fatigue, shortness of breath, and fluid buildup (edema) in the lungs and other parts of the body, like legs, feet, and ankles. Healthcare providers commonly use a classification system called the New York Heart Association (NYHA) functional classification to help guide treatment strategies. This classification system puts you in one of four categories based on how much your symptoms are limiting your physical activity. Classes I–IV range from no limitation of physical activity (class I) to class IV in which you are unable to do any physical activity without being uncomfortable (AHA, 2017).

People with class III-IV heart failure have swelling and trouble breathing from fluid accumulation with little to no physical activity. In this group, spironolactone can help by decreasing edema and the need for hospitalization. But usually, spironolactone cannot treat heart failure by itself, so it is often used with other heart medications.

High blood pressure

High blood pressure, also called hypertension, affects almost half of Americans—in fact, most don’t even realize that they have the condition (AHA, 2017). Treatment is important because high blood pressure increases your risk of heart attacks, strokes, kidney disease, and other problems. Treatment may only entail lifestyle changes, like a healthy, low-sodium diet, regular physical activity, and smoking cessation. 

However, lifestyle changes alone do not work for everyone, and some people need to take prescription blood pressure medications (also called antihypertensive drugs). Spironolactone can help you get rid of excess water, thereby lowering your blood pressure and decreasing the workload on your heart—but it is not usually used as first-line therapy. 

Your healthcare provider will most likely start you on another antihypertensive first, like thiazide diuretics or angiotensin-converting enzyme (ACE) inhibitors. However, these medications may not be effective or be tolerated by some, and spironolactone may be added to the regimen. Talk to your healthcare provider about the best treatment options for you. 

Fluid accumulation (ascites, nephrotic syndrome)

In addition to heart failure, other medical conditions can lead to an accumulation of fluid in the body; these include liver diseases like cirrhosis and kidney problems like nephrotic syndrome. In cirrhosis, your liver is permanently damaged and scarred from other liver conditions, like alcoholic and nonalcoholic liver disease, hepatitis B, and hepatitis C. The scar tissue replaces healthy liver cells, and the liver begins to fail. Liver failure from cirrhosis can lead to a buildup of fluid in your abdomen called ascites (NIDDK, 2018).

Nephrotic syndrome is a medical condition caused by damage to your kidney’s filtering system; this damage can be limited to the kidneys or may be due to a systemic condition like diabetes or lupus. This filtering system plays a vital role in removing waste and excess water. When it fails, you may start to retain water and leak proteins into the urine. Symptoms of nephrotic syndrome include swelling around your eyes as well as in your feet and ankles due to all of the fluid retention (NIDDK, 2014).

Spironolactone can help with the fluid buildup by encouraging the kidney to get rid of sodium and water, thereby decreasing the overall fluid volume in the body.

Primary hyperaldosteronism

Primary hyperaldosteronism is the most common cause of secondary hypertension (hypertension caused by another medical problem). In this condition, your adrenal glands (small glands that sit on top of your kidneys) secrete more aldosterone than they should, either due to abnormal growth or overactivity. 

Aldosterone is responsible for raising blood pressure by increasing sodium and salt retention while excreting potassium. As you can imagine, this can lead to hypertension as well as low potassium levels, both of which can be harmful to the heart. 

Symptoms of hyperaldosteronism include muscle cramps, weakness/fatigue, feeling thirsty all of the time, and urinating frequently. Spironolactone may benefit people with this condition because it encourages the kidneys to excrete water and sodium but keep the potassium.

Low potassium levels (hypokalemia)

Low potassium levels can be dangerous to your heart. Potassium is necessary for heart and nerve cells to work properly—if levels drop too low, problems may arise. Common symptoms of low blood potassium levels include muscle weakness or cramps, fatigue, constipation, and irregular heart rhythms (arrhythmias). As a potassium-sparing diuretic, spironolactone may aid in raising your potassium levels (Mount, 2020).

Off-label

Healthcare providers may prescribe spironolactone for "off-label" use—this means that the FDA hasn't approved spironolactone to treat that specific condition. Most of the "off-label" uses for spironolactone involve its ability to bind to male hormone (androgen) receptors, decreasing the androgen’s activity (UpToDate, n.d.):

• Acne and facial hair (hirsutism) in women: Hormones play an important role in adult acne, especially in women. Hormonal imbalances leading to higher levels of androgens affect women around their periods, during or after pregnancy, menopause (and perimenopause), and when starting or stopping birth control pills. Certain medical conditions, like polycystic ovary syndrome (PCOS), also increase the levels of androgens compared to estrogens and cause hormonal imbalances. Androgens increase the amount of oil produced in the skin and often lead to acne or more prominent facial hair (hirsutism) in women. Spironolactone can help by blocking androgens in the skin, improving acne, and decreasing facial hair growth (Layton, 2017). Spironolactone is generally not used to treat acne in men because it can lead to breast development.

• Hormone therapy for transgender females: Because of spironolactone’s ability to block male hormone activity and testosterone production, it may benefit biological males who transition to female (Angus, 2019).

Common side effects include (UpToDate, n.d.): 

• Gynecomastia: breast tissue enlargement in men in around 9% of men

• Electrolyte imbalances: low sodium (hyponatremia), low magnesium (hypomagnesemia), and low calcium (hypocalcemia)

• High levels of uric acid (uricemia)

• Nipple pain

• Stomach pain

• Nausea/vomiting

• Irregular menstrual periods

• Bleeding after menopause

• Tiredness

• Leg cramps

• Dizziness or lightheadedness

Serious side effects (DailyMed, 2018):

• High potassium levels (hyperkalemia): Spironolactone often raises potassium levels. However, if potassium levels get too high, they can lead to numbness, tingling, and muscle weakness. They can also cause an irregular heartbeat and, in the worst case, heart attacks or death. The risk of high potassium levels increases if you are also taking potassium supplements or other medications that increase potassium, like angiotensin-converting enzyme (ACE) inhibitors. 

• Very low blood pressure (hypotension)

• Worsening kidney function

• Serious allergic reaction (anaphylaxis) or severe skin rashes like Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN)

• Worsening neurological functioning in people with liver disease

This list does not include all possible side effects, and others may occur. Seek medical advice from your pharmacist or healthcare provider for more information.

Talk to your healthcare provider about any other drugs or supplements that you are taking before starting spironolactone, including over-the-counter medications. Potential drug interactions include (DailyMed, 2018):

• Potassium supplements: Potassium supplementation, with salt substitutes containing potassium, potassium supplements, or a diet rich in potassium, may increase your risk of developing life-threatening hyperkalemia.

• Drugs that increase potassium levels: Certain medications increase potassium levels, either as part of the way they work or as a side effect. Combining these medicines with spironolactone can increase your risk of having very high potassium levels. Examples of these drugs include other potassium-sparing diuretics (like amiloride), angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), eplerenone, nonsteroidal anti-inflammatory drugs (NSAIDs), trimethoprim, and heparin.

• Lithium: Spironolactone may decrease the removal of lithium by the kidneys, increasing the potential for lithium toxicity.

• Nonsteroidal anti-inflammatory drugs (NSAIDs): In addition to their effect on potassium, NSAIDs can decrease spironolactone's effectiveness.

• Acetylsalicylic acid (aspirin): Aspirin can decrease spironolactone's effectiveness.

• Digoxin: Spironolactone interferes with some of the tests that measure digoxin levels.

This list does not include all possible drug interactions with spironolactone, and others may occur. Talk to your pharmacist or healthcare provider for more information.

Spironolactone has a higher risk of side effects in certain groups of people. These groups should avoid using spironolactone or use it with caution and careful monitoring. Examples of these groups include (DailyMed, 2018):

• Men: Most healthcare providers use spironolactone with caution in men because of the risk of gynecomastia.

• Pregnant women: There is a risk that spironolactone can interfere with the development of a male fetus because of its effects on male hormones. If you want to take spironolactone during pregnancy, be sure to discuss the risks and benefits with your healthcare provider.

• Women who are breastfeeding: Spironolactone has not been detected in breastmilk. However, because data is limited, lactating women should use spironolactone with caution under the guidance of their healthcare provider.

• Older people: Older people have a higher risk of side effects from spironolactone because kidney function often declines with age. The kidneys are responsible for getting rid of spironolactone; if they do not function properly, too much of the drug will remain in your system. Older people may need an adjusted spironolactone dose.

• People with high potassium levels: Since spironolactone raises potassium levels, you should not take it if you already have elevated potassium. Some medical conditions, like Addison's disease, can increase potassium (UpToDate, n.d.).

• People with gout: Spironolactone may increase your levels of uric acid, leading to an attack of gout in susceptible people (UpToDate, n.d.).

• People with kidney disease: Since the kidneys are responsible for removing spironolactone from the system, people with kidney disease and decreased kidney function may have higher than anticipated levels of the drug in their bodies. They may need an adjusted spironolactone dose.

• People with liver disease: Sudden changes in water or electrolyte levels in people with liver disease, like cirrhosis or ascites, can trigger neurological problems or coma. They may need an adjusted spironolactone dose.

Spironolactone tablets come in 25 mg, 50 mg, and 100 mg strengths in both generic and brand name (Aldactone) formulations. The oral spironolactone suspension (brand name Carospir) may be helpful for people with trouble swallowing. Most people take spironolactone once or twice per day. For some people, it may take two weeks or longer for the drug to take full effect (MedlinePlus, 2018). Most insurance plans cover spironolactone; it usually costs around $6–$12 for a 30-day supply (GoodRx, n.d.).

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

September 14, 2020

Written by

Mike Bohl, MD, MPH, ALM

Fact checked by

Chimene Richa, MD

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About the medical reviewer

Chimene Richa, MD

Dr. Richa is a board-certified Ophthalmologist and medical writer for Ro.