Co-amilozide

How it works

Hydrochlorothiazide inhibits sodium-chloride reabsorption in the distal convoluted tubule, while amiloride blocks epithelial sodium channels to reduce the associated potassium loss.

Prescribing in practice

• Monitor for hyperkalaemia from the amiloride component, particularly in renal impairment or with ACE inhibitors, ARBs or potassium supplements.
• Thiazides can cause hyponatraemia, hypomagnesaemia, hyperglycaemia, hyperuricaemia and may precipitate gout.
• Avoid in significant renal impairment and do not combine with other potassium-sparing agents or potassium supplements.

Monitoring

Monitor serum electrolytes including potassium and sodium, with renal function and blood pressure.

Counselling the patient

• Take the dose in the morning to reduce night-time urination.
• Report palpitations, muscle weakness, confusion or marked dizziness.
• Avoid potassium-containing salt substitutes unless advised.

Evidence & guidelines

Thiazide-type diuretics are an established option in NICE hypertension guidance; the potassium-sparing combination is used to offset thiazide-induced hypokalaemia.