BMA Concise Guide to Medicine & Drugs


Brand name Aldactone

Used in the following combined preparations Aldactide, Lasilactone


Drug group Potassium-sparing diuretic

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic Yes


Spironolactone belongs to the class of drugs know as potassium-sparing diuretics. It is used alone or in combination with thiazide or loop diuretics in the treatment of oedema (fluid retention) resulting from congestive heart failure, cirrhosis of the liver, and nephrotic syndrome (a kidney disorder). It is also used to reduce blood pressure, especially in people with Conn’s syndrome, a condition caused by a benign tumour in one of the adrenal glands.

Spironolactone is relatively slow to act, and its effects may appear only after several days of treatment. As with other potassium-sparing diuretics, there is a risk of unusually high levels of potassium in the blood if the kidneys are functioning abnormally. For this reason, the drug is prescribed with caution to people with kidney failure.

Spironolactone does not worsen gout or diabetes, as do some other diuretics. The major side effect is nausea, but abnormal breast enlargement (gynaecomastia) may occur in men.


Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, capsules, liquid.

Frequency and timing of doses Once daily, usually in the morning.

Adult dosage range 25–400mg daily.

Onset of effect Within 1–3 days, but full effect may take up to 2 weeks.

Duration of action 2–3 days.

Diet advice Avoid foods that are high in potassium, for example, dried fruit and salt substitutes.

Storage Keep in original container at room temperature out of the reach of children. Protect from light.

Missed dose Take as soon as you remember.

Stopping the drug Do not stop the drug without consulting your doctor; symptoms may recur.

Exceeding the dose An occasional unintentional extra dose is unlikely to be a cause for concern. But if you notice any unusual symptoms, or if a large overdose has been taken, notify your doctor.


Spironolactone has few common adverse effects, the chief ones being nausea and vomiting. The main problem is the possibility that potassium may be retained by the body, causing muscle weakness and numbness. Consult your doctor if these symptoms occur. Rarely, the drug may cause headache, lethargy, drowsiness, and irregular menstruation; discuss with your doctor if these are severe. In men, it may also cause breast enlargement or tenderness and erectile dysfunction (impotence); if so, consult your doctor. If a rash develops (in either sex), stop taking the drug and contact your doctor immediately.


ACE inhibitors, NSAIDs, angiotensin II blockers, ciclosporin, tacrolimus, and potassium salts These drugs may increase the risk of raised blood levels of potassium, and can enhance the lowering of blood pressure caused by spironolactone.

Lithium Spironolactone may increase the blood levels of lithium, leading to an increased risk of lithium toxicity.

Digoxin Adverse effects may result from increased digoxin levels.


Be sure to tell your doctor if:

· You have long-term liver or kidney problems.

· You have porphyria.

· You have Addison’s disease.

· You have a metabolic disorder.

· You are taking other medicines.

Pregnancy Not usually prescribed. May have adverse effects on the baby. Discuss with your doctor.

Breast-feeding The drug passes into the breast milk, but at normal doses adverse effects on the baby are unlikely. Discuss with your doctor.

Infants and children Reduced dose necessary.

Over 60 Increased likelihood of adverse effects. Reduced dose may therefore be necessary.

Driving and hazardous work Avoid such activities until you have learned how spironolactone affects you because the drug may occasionally cause drowsiness.

Alcohol No known problems.


Long-term use in the young is avoided if possible.

Monitoring Blood tests may be performed to check on kidney function and levels of body salts.