Spironolactone: uses, dosing, side effects & brands

Carospir (Spironolactone) is an aldosterone antagonist used to treat Ascites, Edema, Heart Failure, Hirsutism.

The FDA classifies spironolactone as an aldosterone antagonist. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.

The elimination half-life of spironolactone is about 1.4 hours — that is how long the body takes to clear half of a dose. The parent drug clears fast, but that number is misleading on its own: spironolactone is rapidly and extensively metabolized (mainly by CYP3A4/5, less by CYP2C8) into active metabolites that far outlast it. Canrenone has a mean half-life of 16.5 hours, 7-alpha-(thiomethyl)spirolactone (TMS) 13.8 hours, and 6-beta-hydroxy-7-alpha-(thiomethyl)spirolactone (HTMS) 15 hours — these metabolites are themselves aldosterone antagonists, so the drug's effect persists long after the parent is gone. The Aldactone label states the impact of age, sex, race/ethnicity, and renal impairment on spironolactone pharmacokinetics has NOT been specifically studied, so no labeled numbers exist for older adults or kidney impairment. In hepatic impairment the label does report that the terminal half-life is increased in patients with cirrhotic ascites, without giving a figure. There is no extended-release spironolactone in the US; the one alternative formulation, CaroSpir oral suspension, is immediate-release and lists a similar parent half-life of roughly 1 to 2 hours with metabolite half-lives of 10 to 35 hours, though it is not interchangeable with tablets (15-37% higher serum concentration at an equivalent dose). Food roughly doubles absorption (AUC up about 90-95%), which is why intake should be kept consistent relative to meals. Half-life is not the same as how long a drug test can detect the drug, and it varies with age, kidney and liver function.

It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run spironolactone against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.

We track 2 spironolactone-containing products in the U.S.: Carospir and Spironolactone. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.

Across the brands we track, spironolactone is currently marketed as suspension and tablet, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.

Yes. Our catalog lists 1 generic spironolactone product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.

The FDA's Enforcement database lists 1 recall record whose product description mentions spironolactone. The most recent: Spironolactone Tablets (Aug 5, 2025). A recall applies to specific lots, not to the drug as a whole — check the record for the affected lot numbers.

For fluid retention or blood pressure, spironolactone's diuretic effect begins within a day or two. But the use most people ask about, hormonal acne or female-pattern hair loss, is slow: this off-label use typically takes about 8 to 12 weeks, sometimes longer, before skin or hair visibly improves. Keep taking it daily and don't expect an overnight change.

Because Aldactone (spironolactone) blocks aldosterone and holds onto potassium while flushing out water and salt, Common effects include increased urination and dizziness; MedlinePlus additionally lists drowsiness or tiredness, stomach pain, vomiting or diarrhea, and hormone-related changes: breast enlargement or tenderness in men and women, irregular menstrual periods, and, in men, erectile dysfunction. Many are dose-related. This is not a complete list — ask your pharmacist about your specific dose.

The one you must not miss is hyperkalemia (high blood potassium), which can trigger dangerous, even fatal, heart rhythm changes. The FDA label warns: 'ALDACTONE can cause hyperkalemia. This risk is increased by impaired renal function or concomitant potassium supplementation, potassium-containing salt substitutes or drugs that increase potassium, such as [ACE inhibitors] and [ARBs].' MedlinePlus says to call your doctor immediately for 'muscle weakness, pain, or cramps; ... numbness, or tingling in the hands or feet; inability to move arms or legs; changes in heartbeat; confusion; nausea; extreme tiredness.' Seek emergency care for irregular heartbeat or fainting.

Yes. Aldactone (spironolactone) makes your body keep potassium, so adding more can push you into dangerous hyperkalemia. Per the FDA label, the risk rises with 'potassium supplementation' and 'potassium-containing salt substitutes' — most 'lite' or 'no-salt' substitutes are potassium chloride. MedlinePlus advises avoiding potassium-containing salt substitutes and checking with your doctor before eating large amounts of potassium-rich foods. Your prescriber will also check a blood potassium level, typically within a week of starting or changing the dose.

It can. Gynecomastia (breast tissue enlargement in men) is a recognized hormonal effect because spironolactone has anti-androgen activity. In the RALES heart-failure trial cited in the FDA label, about 9% of men developed gynecomastia at a mean dose of ~26 mg daily, and the label describes it as 'usually reversible' — it often improves after the drug is stopped. Aldactone also carries a boxed warning that it 'has been shown to be a tumorigen in chronic toxicity studies in rats,' so it should be used only for its approved indications. Do not stop it on your own; discuss breast changes with your prescriber.

The diuretic effect — more urination — usually begins within hours to a couple of days, though the full blood-pressure or fluid benefit builds over about two weeks. Potassium can rise soon after starting or after a dose increase, which is why blood tests are done early. Hormonal effects like breast tenderness or menstrual changes tend to appear over weeks and often ease after stopping. Kidney disease raises the hyperkalemia risk, so those patients need clearance and closer monitoring.

Spironolactone is FDA-approved to treat high blood pressure, heart failure, and fluid retention (edema) caused by heart failure, liver cirrhosis, or kidney disease. It also treats primary hyperaldosteronism (a hormone disorder) and low potassium levels. It's a potassium-sparing diuretic ("water pill") that works by blocking the hormone aldosterone, so the body releases water and sodium while holding on to potassium.

Yes, but off-label — these are not FDA-approved uses. Because spironolactone blocks androgens (male-type hormones), doctors commonly prescribe it off-label for hormonal acne, excess facial or body hair (hirsutism), and PCOS-related symptoms in women. Evidence supports these uses, but they aren't on the FDA label, and spironolactone isn't used this way in men because it can cause breast tissue growth (gynecomastia).

Because it makes the body retain potassium, spironolactone can raise potassium to dangerous levels (hyperkalemia), especially in people with kidney problems or those taking ACE inhibitors, ARBs, or potassium supplements. The FDA label advises checking potassium and kidney function periodically, and avoiding potassium-based salt substitutes without medical guidance.