Mineralocorticoid receptor antagonists · Cardiovascular
Spironolactone
Aldactone®(brand names vary by market)
A weak diuretic with a strong survival benefit, and a potassium you must watch.
Mechanism
Competitive aldosterone receptor antagonist in the distal nephron and collecting duct: modest sodium loss, potassium retention, and blocked cardiac and vascular fibrosis.
Open the interactive pathwayIndications
- Heart failure with reduced ejection fraction
- Resistant hypertension
- Ascites and oedema in cirrhosis
- Primary aldosteronism
- Acne and hirsutism (anti-androgen effect)
Formulations
Dosing concepts
Heart failure
The dose that improves survival is small and is not titrated for diuresis. Pushing it upward chasing urine output is how hyperkalemia is manufactured.
Cirrhotic ascites
Here it is a genuine diuretic and the doses are far larger, usually paired with furosemide in a fixed ratio to keep potassium steady.
Renal function
Generally avoided once eGFR falls below about 30, and stopped during any acute illness with vomiting or diarrhoea.
Concepts, not prescribing instructions. Practice numbers live in current references and local protocols.
Pharmacokinetics
- Bioavailability
- ~65% with food
- Half-life
- ~1.4 h for the parent, but active metabolites persist for 15 to 20 h
- Elimination
- hepatic: Canrenone and other active metabolites carry most of the effect
- Protein binding
- >90%
Adverse effects
- Hyperkalemiacommon & seriousThe dose-limiting and occasionally lethal effect, especially alongside RAAS blockade or an acute illness.
- Gynecomastia and breast tendernesscommonOff-target androgen and progesterone receptor binding; the usual reason men switch to eplerenone.
- Acute kidney injury when volume-depleteserious
- Menstrual irregularitycommon
- Metabolic acidosis in advanced CKDserious
Contraindications & precautions
Contraindications
- Hyperkalemia
- Severe renal impairment
- Addison disease
- Concurrent eplerenone or potassium supplements without a clear plan
Precautions
- Any RAAS blockade
- Trimethoprim, which behaves like a potassium-sparing diuretic
- Diarrhoeal illness
- NSAIDs
Interactions
- ACE inhibitors / ARBs + Potassium-sparing diuretics, K supplements, salt substitutescautionAdditive hyperkalemia, worst with renal impairment layered on top.
- ACE inhibitor / ARB + diuretic + NSAID (the 'triple whammy')avoidAcute kidney injury, classically in a dehydrated older adult who bought ibuprofen for a sore knee.
Monitoring
Potassium and creatinine
The whole safety profile in two numbers · Baseline, 1 week, 4 weeks, then every 3 to 6 months, and sooner after any change or illness
Weight and congestion in heart failure
Effect
Breast symptoms in men
Common, distressing, and switchable
Counselling points
- You will need blood tests soon after starting and after any dose change; they are not optional.
- Stop it and contact us if you develop vomiting or diarrhoea, and get your bloods checked.
- Avoid salt substitutes, which are usually potassium.
- Men: tell us about any breast tenderness or swelling, there is an alternative.
Clinical pearls
- The classic serious harm is a patient on an ACE inhibitor and spironolactone who gets gastroenteritis, keeps taking both, and arrives with a potassium of seven. Sick-day rules are the intervention.
- In heart failure it is a survival drug that happens to be a diuretic. In cirrhosis it is a diuretic. Same molecule, different intent, different dose entirely.
References & review
- Spironolactone product monograph (consult the current version for your market) (monograph)
- Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed. (reference-work)
Last reviewed 2026-08-16 · jurisdiction: global · drug information changes; verify against current references before practice use.