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Diuretic Pregnancy: Teratogenic and embryotoxic potential in humans is unknown; should not be used in pregnancy unless benefits outweigh possible risk to the foetus (which includes persistence of patent ductus arteriosus). May pass into breast milk or inhibit lactation — use with caution in nursing mothers (contraindicated in breast-feeding women per section 4.3).

Furosemide

Brand names: Lasix, Frusemide

Used in: Heart Failure Chronic Kidney Disease Liver Disease & Cirrhosis Acute Kidney Injury

Furosemide is a loop diuretic used to relieve fluid overload in heart failure, pulmonary oedema, renal and hepatic disease, and to treat resistant hypertension.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Oedema: initially 40 mg in the morning (maintenance 20 mg daily or 40 mg on alternate days)
Route: oral
Frequency: once daily (morning), adjusted to response
Max: Resistant oedema up to 80 mg daily; chronic renal insufficiency up to 1,500 mg/24 h (exceptionally up to 2,000 mg/24 h)
Adults and children over 12 years. Oedema: initially 40 mg daily in the morning; maintenance 20 mg daily or 40 mg on alternate days, increased in resistant oedema to 80 mg daily. Hypertension: 20–40 mg twice daily; if 40 mg twice daily is inadequate, add other antihypertensives rather than increase the furosemide dose. Chronic renal insufficiency: initial daily dose 250 mg, increased in steps of 250 mg at 4–6 hourly intervals up to a maximum 1,500 mg/24 h (exceptionally up to 2,000 mg/24 h). Elderly: eliminated more slowly — titrate to response. Children under 12 years (per SPC): 1–3 mg/kg body weight daily, max total 40 mg/day — verify paediatric dosing against a children's formulary.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to furosemide, any excipient, sulphonamides or sulphonamide derivatives/amiloride
  • Anuria and impaired renal function (creatinine clearance below 30 mL/min per 1.73 m2) and renal failure from nephrotoxic/hepatotoxic poisoning
  • Severe hypokalaemia, severe hyponatraemia, hypovolaemia, dehydration and/or hypotension
  • Concomitant potassium supplements or potassium-sparing diuretics
  • Pre-coma/coma associated with hepatic cirrhosis or encephalopathy
  • Addison's disease
  • Digitalis intoxication
  • Breast-feeding women

Side effects

  • Thrombocytopenia (uncommon)
  • Cardiac arrhythmias (uncommon); reduction in blood pressure
  • Deafness (sometimes irreversible), tinnitus (uncommon/rare)
  • Dry mouth, nausea, vomiting, diarrhoea, constipation (uncommon)
  • Electrolyte and water disturbance (hypokalaemia, hyponatraemia, hypocalcaemia, hypomagnesaemia); metabolic acidosis

Interactions

  • ACE inhibitors / angiotensin II receptor blockers — marked falls in blood pressure and possible impaired renal function; stop or reduce furosemide before starting an ACE inhibitor
  • Antihypertensives — enhanced hypotensive effect
  • Post-synaptic alpha blockers (e.g. prazosin) — risk of first-dose hypotensive effect
  • Antipsychotics — furosemide-induced hypokalaemia increases risk of cardiac toxicity; avoid pimozide; increased ventricular arrhythmia risk with amisulpride
  • Colestyramine and colestipol — administer 2 to 3 hours apart

Clinical monograph

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.

Reference: NICE NG106 Chronic HF; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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