Potassium-sparing diuretic (epithelial Na+ channel blocker) Pregnancy: Not recommended during pregnancy or lactation; potential benefits must be weighed against possible hazards to the foetus.

Amiloride hydrochloride

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

Amiloride is a weak potassium-sparing diuretic, usually combined with a thiazide or loop diuretic to counteract potassium loss.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Initially 10 mg daily or 5 mg twice daily, adjusted according to response

Route: Oral

Frequency: Once or twice daily

Max: 20 mg daily

As adjunct to other diuretics for hypertension and congestive heart failure: initially 5 mg or 10 mg daily. Cirrhosis with ascites: initially 5 mg daily. Elderly: adjust dose according to renal function, blood electrolytes and diuretic response. Not indicated in children under 18 years.

Dose adjustments

Renal

Contraindicated in severe renal impairment; monitor serum electrolytes and blood urea in patients with impaired renal function.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

DOSAGE AND ADMINISTRATION Amiloride HCl should be administered with food. Amiloride HCl, one 5 mg tablet daily, should be added to the usual antihypertensive or diuretic dosage of a kaliuretic diuretic. The dosage may be increased to 10 mg per day, if necessary. More than two 5 mg tablets of amiloride HCl daily usually are not needed, and there is little controlled experience with such doses. If persistent hypokalemia is documented with 10 mg, the dose can be increased to 15 mg, then 20 mg, with careful monitoring of electrolytes. In treating patients with congestive heart failure after an initial diuresis has been achieved, potassium loss may also decrease and the need for amiloride HCl …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2023-11-28. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Hyperkalaemia
Severe renal impairment
Prior sensitivity to amiloride
Concurrent other potassium-sparing drugs or potassium supplements

Side effects

Hyperkalaemia (particularly in elderly, diabetics, renal impairment)
Hyponatraemia
Nausea, vomiting, constipation or diarrhoea, abdominal pain
Postural hypotension, dizziness
Rash, pruritus

Interactions

ACE inhibitors and angiotensin-II antagonists — enhanced hypotensive effect and increased risk of hyperkalaemia
NSAIDs (e.g. indometacin) — increased risk of hyperkalaemia and nephrotoxicity; may antagonise diuretic effect
Lithium — reduced renal clearance, high risk of lithium toxicity
Other antihypertensives (calcium channel blockers, beta blockers, alpha blockers, hydralazine) — enhanced hypotensive effect
Quinidine — antiarrhythmic activity opposed by amiloride

Clinical monograph

How it works

It blocks epithelial sodium channels in the distal nephron, promoting modest sodium loss while reducing potassium and hydrogen excretion.

Prescribing in practice

Hyperkalaemia is the key risk—avoid with ACE inhibitors, ARBs, potassium supplements or other potassium-sparing drugs, and use with particular caution in renal impairment or diabetes.
Check renal function and potassium before starting and after dose changes.
It is most often used in fixed or separate combination to offset the potassium loss caused by a thiazide or loop diuretic.

Monitoring

Monitor serum potassium and renal function before starting, after dose changes and periodically thereafter, with closer review if other potassium-affecting drugs are added.

Counselling the patient

Avoid potassium-based salt substitutes and do not take potassium supplements unless specifically advised.
Report muscle weakness, numbness or an irregular heartbeat, which can be signs of a high potassium level.

Evidence & guidelines

Established potassium-sparing diuretic used adjunctively in hypertension and oedema.

Reference: SmPC Co-amilofruse; NICE NG106 (Chronic HF 2018); KDIGO Hyperkalaemia Guidance; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways