Furosemide

How it works

It inhibits the sodium-potassium-chloride co-transporter in the thick ascending limb of the loop of Henle, producing a potent diuresis with loss of sodium, potassium, chloride, calcium and magnesium.

Prescribing in practice

• It can cause hypokalaemia, hyponatraemia, hypovolaemia and acute kidney injury, so electrolytes and renal function must be monitored, particularly with other diuretics, ACE inhibitors or NSAIDs.
• High doses or rapid intravenous administration, especially in renal impairment, carry a risk of ototoxicity that is increased with other ototoxic drugs.
• It may precipitate or worsen gout and can unmask urinary retention in men with prostatic enlargement.

Monitoring

Check renal function and electrolytes, along with fluid status and weight, especially after starting or up-titrating.

Counselling the patient

• The medicine increases urine output, so taking it earlier in the day avoids night-time disturbance.
• Report muscle cramps, marked dizziness or a notable change in how much you pass urine.

Evidence & guidelines

Loop diuretics such as furosemide are a guideline cornerstone for symptomatic relief of congestion in heart failure.