ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Potassium-sparing diuretic (epithelial Na+ channel blocker) Pregnancy: Avoid unless essential — limited data; volume depletion may compromise placental perfusion.

Amiloride hydrochloride

Brand names: Co-amilofruse (with furosemide), Co-amilozide (with hydrochlorothiazide)

Adult dose

Dose: 5–10 mg OD; in HF or hepatic ascites with K-loss: 5–20 mg/day. Often given as a fixed-dose combination (co-amilofruse 5/40 or 10/80) for simpler dosing.
Route: Oral
Frequency: Once daily
Max: 20 mg/day
Take in the morning to avoid nocturia. Monitor U&Es 1 week after start.

Dose adjustments

Renal

Avoid if eGFR <30 ml/min (hyperkalaemia risk). Caution and dose reduction in mild–moderate impairment.

Hepatic

Caution in severe impairment.

Clinical pearls

  • Useful in patients with persistent hypokalaemia on loop or thiazide diuretics — co-amilofruse 5/40 a common single-tablet option.
  • Alternative to spironolactone if androgenic side effects (gynaecomastia, menstrual disturbance).
  • First-line specific therapy for Liddle syndrome (rare cause of hypertension and hypokalaemia).
  • Avoid in advanced CKD — even modest renal impairment markedly raises hyperkalaemia risk.
  • Routinely check K+ and creatinine 1 week after start, after every dose change, and 6-monthly thereafter.

Contraindications

  • Hyperkalaemia (K+ >5.5 mmol/L)
  • Severe renal failure (eGFR <30) or anuria
  • Acute kidney injury
  • Addison's disease / primary adrenal insufficiency
  • Concomitant use of other K-sparing diuretics or K supplements
  • Hyponatraemia, hypovolaemia

Side effects

  • Hyperkalaemia (especially with ACEi/ARB, NSAIDs, or in CKD)
  • Hyponatraemia
  • Dehydration, postural hypotension
  • Raised urea and creatinine
  • GI upset: nausea, abdominal pain
  • Headache, dizziness
  • Rash (uncommon)

Interactions

  • ACEi / ARB / sacubitril-valsartan / spironolactone: additive hyperkalaemia
  • K supplements / salt substitutes (KCl): contraindicated combination
  • NSAIDs: ↓ effect, ↑ AKI risk, ↑ K
  • Lithium: ↓ clearance — toxicity risk
  • Tacrolimus / ciclosporin: ↑ hyperkalaemia

Monitoring

  • U&Es 1 week after start, then 3–6 monthly
  • BP (in hypertension indication)
  • Weight (in HF or ascites indication)

Reference: BNF 90; SmPC Co-amilofruse; NICE NG106 (Chronic HF 2018); KDIGO Hyperkalaemia Guidance. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Pathways