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Aldosterone antagonist (potassium-sparing diuretic) Pregnancy: Avoid — anti-androgenic effects may feminise male fetus.

Spironolactone

Brand names: Aldactone

Adult dose

Dose: HFrEF: 25–50 mg once daily; Ascites: 100–400 mg daily; Primary hyperaldosteronism: 100–400 mg
Route: Oral
Frequency: Once daily
Max: 400 mg/day (ascites/hyperaldosteronism); 50 mg/day (HFrEF)
HF with reduced EF (post-RALES): start 25 mg OD (if creatinine <220 mcmol/L, K+ <5.0). Increase to 50 mg OD if tolerated. RALES trial: 30% reduction in mortality in NYHA III–IV HFrEF. Check potassium 1 and 4 weeks after start.

Paediatric dose

Dose: 1 mg/kg
Route: Oral
Frequency: Once or twice daily
Max: 3 mg/kg/day (max 100 mg/day)
Neonates–12 years: 1–3 mg/kg/day in 1–2 divided doses. Adolescents: adult dose.

Dose adjustments

Renal

Avoid if eGFR <30 (severe hyperkalaemia risk). Use with caution eGFR 30–60.

Hepatic

Use with caution in hepatic impairment (electrolyte disturbance can precipitate encephalopathy).

Paediatric weight-based calculator

Neonates–12 years: 1–3 mg/kg/day in 1–2 divided doses. Adolescents: adult dose.

Clinical pearls

  • RALES trial: significantly reduced mortality in severe HFrEF — standard of care
  • EMPHASIZE-HF (eplerenone) — alternative with fewer hormonal side effects if gynaecomastia occurs
  • Potassium must be <5.0 before starting; check K+ at 1 week, 1 month, then 3-monthly
  • Avoid concurrent K+ supplements and K+-sparing medications
  • Eplerenone (selective aldosterone antagonist) has fewer hormonal side effects — use if gynaecomastia troublesome

Contraindications

  • Hyperkalaemia
  • Addison's disease
  • eGFR <30

Side effects

  • Hyperkalaemia (serious — monitor potassium closely)
  • Gynaecomastia and breast tenderness (antiandrogen effect)
  • Menstrual irregularity (premenopausal)
  • Erectile dysfunction
  • Hyponatraemia
  • Nausea and GI upset

Interactions

  • ACE inhibitors/ARBs — hyperkalaemia risk (AVOID triple whammy: ACEi/ARB + spironolactone + K+ supplements)
  • NSAIDs — reduced efficacy and increased hyperkalaemia risk
  • Digoxin — reduced clearance; toxicity risk

Monitoring

  • U&E (potassium, sodium, creatinine) — 1 week and 4 weeks after start, then 3-monthly
  • Gynecomastia symptoms

Reference: BNFc; BNF; RALES trial; NICE NG106; ESC HF Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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