Triamterene

How it works

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

Prescribing in practice

• It can cause hyperkalaemia, especially in renal impairment or when combined with ACE inhibitors, angiotensin receptor blockers, potassium supplements or other potassium-sparing drugs.
• Avoid in significant renal impairment and in pre-existing hyperkalaemia.
• It may cause a harmless blue discolouration of the urine and rarely contributes to renal stones.

Monitoring

Monitor serum potassium and renal function, particularly in older patients and those on interacting drugs.

Counselling the patient

• Avoid potassium-containing salt substitutes unless advised otherwise.
• Report muscle weakness, palpitations or numbness, which can indicate high potassium.
• Your urine may appear bluish, which is harmless.

Evidence & guidelines

Potassium-sparing diuretics are used to offset potassium loss from thiazide or loop diuretics in line with established practice.