Furosemide with triamterene

How it works

Furosemide blocks the loop-of-Henle sodium-potassium-chloride co-transporter for potent natriuresis, while triamterene blocks distal epithelial sodium channels to reduce potassium excretion, offsetting the potassium-wasting effect of the loop component.

Prescribing in practice

• The triamterene component can cause hyperkalaemia, so the combination should be avoided with other potassium-sparing agents, potassium supplements, ACE inhibitors, ARBs or in significant renal impairment, with potassium closely monitored.
• It can still cause volume depletion, hyponatraemia and acute kidney injury, and the loop component retains a dose-related risk of ototoxicity.
• Triamterene may cause a rise in serum creatinine and, rarely, crystalluria, so adequate hydration and renal monitoring are advised.

Monitoring

Monitor serum potassium and other electrolytes, renal function and fluid status, especially at initiation and after dose change.

Counselling the patient

• Do not use potassium-containing salt substitutes or take potassium supplements unless advised.
• Take the dose earlier in the day to limit night-time urination.
• Report muscle weakness, palpitations or significant dizziness.

Evidence & guidelines

Combining a loop diuretic with a potassium-sparing agent is an established strategy to achieve diuresis while mitigating hypokalaemia.