Amiloride — NZ Medication Guide

What is Amiloride?

Amiloride (generic name: amiloride hydrochloride) is a medication used primarily for oedema prevention and hypertension, particularly as a potassium-sparing diuretic. Amiloride is available in New Zealand in combination with hydrochlorothiazide (Moduretic) funded on the Pharmaceutical Schedule. Amiloride alone is also available but less commonly prescribed.

In New Zealand, amiloride is most commonly prescribed as the combination tablet Moduretic (amiloride 5mg + hydrochlorothiazide 50mg) for management of hypertension and oedema. It is particularly useful for preventing hypokalaemia in patients requiring thiazide diuretics who cannot tolerate potassium supplementation. BPAC NZ recommends caution with potassium-sparing diuretics in patients with chronic kidney disease due to hyperkalaemia risk.

What is Amiloride Used For?

Amiloride is prescribed by healthcare professionals in New Zealand for the following indications:

• Oedema in heart failure — used with thiazide or loop diuretics to spare potassium
• Hypertension (adjunct to other antihypertensives)
• Prevention of hypokalaemia caused by thiazide or loop diuretics
• Primary hyperaldosteronism (Conn’s syndrome) — adjunct management
• Liddle syndrome (rare genetic disorder)

How Does Amiloride Work?

Amiloride is a potassium-sparing diuretic that blocks sodium channels in the distal nephron (epithelial sodium channels, ENaC), reducing sodium reabsorption independently of aldosterone. Unlike spironolactone, amiloride does not act through aldosterone receptors. This causes mild sodium and water excretion (diuresis) while retaining potassium, making it useful for preventing diuretic-induced hypokalaemia.

How to Take Amiloride

Take amiloride with food to reduce gastrointestinal discomfort. It is usually combined with a thiazide diuretic (e.g., in Moduretic — amiloride + hydrochlorothiazide) or a loop diuretic. Avoid high-potassium foods and potassium supplements unless specifically directed by your doctor — amiloride retains potassium and hyperkalaemia can be dangerous. Regular blood tests to monitor kidney function and potassium levels are required.

Common Side Effects

Like all medications, Amiloride may cause side effects. Common side effects include:

• Hyperkalaemia (high potassium) — risk increases with renal impairment
• Nausea and abdominal discomfort
• Headache
• Dizziness
• Muscle cramps
• Mild rash

Serious Side Effects — Seek Medical Attention

Contact your doctor or call 111 immediately if you experience any of the following serious effects:

• Severe hyperkalaemia — dangerous heart rhythm disturbances
• Acute kidney injury — particularly in dehydrated patients or those on ACE inhibitors
• Hyponatraemia (low sodium)
• Metabolic acidosis in patients with impaired kidney function

Drug Interactions

Always inform your prescriber and pharmacist of all medications, supplements, and herbal products you are taking. Notable interactions with Amiloride include:

• ACE inhibitors and ARBs — combined potassium-retaining effect; high hyperkalaemia risk
• Potassium supplements — CONTRAINDICATED with amiloride (hyperkalaemia risk)
• NSAIDs — reduce diuretic effect and worsen kidney function
• Trimethoprim/co-trimoxazole — additive potassium retention risk
• Digoxin — amiloride does not increase digoxin levels but hyperkalaemia may affect digoxin action

New Zealand Prescribing Information

In New Zealand, amiloride is most commonly prescribed as the combination tablet Moduretic (amiloride 5mg + hydrochlorothiazide 50mg) for management of hypertension and oedema. It is particularly useful for preventing hypokalaemia in patients requiring thiazide diuretics who cannot tolerate potassium supplementation. BPAC NZ recommends caution with potassium-sparing diuretics in patients with chronic kidney disease due to hyperkalaemia risk.

Frequently Asked Questions

Can I eat bananas or potassium-rich foods while on amiloride?

You should avoid excessive potassium intake while taking amiloride, as this medication already retains potassium in the body. High-potassium foods include bananas, oranges, tomatoes, potatoes, and spinach. This does not mean you must completely avoid these foods, but you should not increase your consumption significantly. Do not take potassium supplements or salt substitutes containing potassium without medical advice.

Why am I taking amiloride with another diuretic?

Amiloride on its own is a weak diuretic. Its main value is in preventing the potassium loss caused by stronger diuretics like furosemide or hydrochlorothiazide. By combining them, you get effective fluid removal while protecting potassium levels. This combination is particularly useful in heart failure and hypertension management.

References & Further Information

The following New Zealand and international resources were used to inform this page:

• New Zealand Formulary — Amiloride
• Pharmac — Funded Medicines Schedule
• BPAC NZ — Managing Hypertension
• Medsafe — Moduretic Data Sheet

Reviewed by a Registered Pharmacist — KiwiMeds New Zealand