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Potassium-Sparing Diuretic / Mineralocorticoid Receptor Antagonist Pregnancy: Avoid — anti-androgenic effects may feminise male fetus; limited data

Spironolactone

Brand names: Aldactone

Adult dose

Dose: Heart failure: 25–50 mg OD. Primary hyperaldosteronism: 100–400 mg OD. Ascites: 100–400 mg OD. Acne/hirsutism (off-label): 25–100 mg OD–BD.
Route: Oral
Frequency: Once daily (or BD for high doses)
Max: 400 mg/day
Anti-androgenic effects — gynecomastia and menstrual irregularities common. Check K+ and renal function 1 week after starting or dose changes. RALES trial.

Paediatric dose

Dose: 1 mg/day/kg
Route: Oral
Frequency: OD–BD
Max: As per indication and response
Concentration: 25 mg/5 mL oral suspension mg/day/ml
Children: 1–3.3 mg/kg/day in 1–2 divided doses. Used for diuresis in heart failure, liver disease, nephrotic syndrome.

Dose adjustments

Renal

Avoid if eGFR <30 — hyperkalaemia risk. Maximum 25 mg OD if eGFR 30–60.

Hepatic

No dose adjustment; used for cirrhotic ascites (100–400 mg OD)

Paediatric weight-based calculator

Children: 1–3.3 mg/kg/day in 1–2 divided doses. Used for diuresis in heart failure, liver disease, nephrotic syndrome.

Clinical pearls

  • RALES trial: 30% mortality reduction in severe HFrEF (NYHA III–IV, LVEF <35%)
  • Gynecomastia occurs in 5–15% of men — if problematic, switch to eplerenone (selective MRA)
  • For ascites: start spironolactone 100 mg OD, may add furosemide 40 mg OD; titrate in 100/40 ratio (spironolactone/furosemide)
  • Check electrolytes and renal function 1 week after any dose change — particularly in patients on ACEi/ARB

Contraindications

  • Hyperkalaemia (K+ >5.5 mmol/L)
  • Addison's disease
  • Severe renal impairment
  • Concomitant eplerenone

Side effects

  • Gynecomastia (dose-dependent — 5–15%)
  • Menstrual irregularities
  • Hyperkalaemia
  • Nausea
  • Breast tenderness
  • Dizziness
  • Renal impairment

Interactions

  • ACEi/ARBs — significant hyperkalaemia risk
  • NSAIDs — reduced diuretic effect and renal impairment
  • Digoxin — increased digoxin levels (reduced clearance)
  • Lithium — increased lithium toxicity

Monitoring

  • Serum potassium (1 week and 4 weeks after starting, then 3-monthly)
  • Renal function (eGFR, creatinine)
  • Breast tenderness and gynaecomastia
  • Blood pressure and weight

Reference: BNFc; BNF; RALES Trial (Pitt et al, NEJM 1999); ESC Heart Failure Guidelines 2021. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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