Furosemide

How it works

It inhibits the sodium-potassium-chloride co-transporter in the thick ascending limb of the loop of Henle, producing potent natriuresis and diuresis.

Prescribing in practice

• It can cause electrolyte disturbance, most notably hypokalaemia, along with hyponatraemia, hypomagnesaemia and dehydration with prerenal kidney injury.
• Ototoxicity may occur, particularly with rapid intravenous administration, high doses or co-administration with other ototoxic drugs such as aminoglycosides.
• It can precipitate or worsen gout and may unmask urinary retention in men with prostatic enlargement.

Monitoring

Monitor renal function, electrolytes and fluid status, particularly on initiation, dose changes and during intercurrent illness.

Counselling the patient

• Take in the morning to avoid disturbed sleep from passing urine at night.
• Report muscle cramps, dizziness, marked thirst or confusion, which may signal salt or water imbalance.
• Weigh yourself regularly if advised, to help track fluid balance.

Evidence & guidelines

Furosemide is the standard loop diuretic in NICE heart failure and chronic kidney disease guidance for symptomatic relief of congestion.