Diuretic Pregnancy: C — avoid in first trimester. Use in later pregnancy only for pulmonary oedema.

Furosemide

Brand names: Lasix, Frusemide

Adult dose

Dose: Acute HF/pulmonary oedema: 40–80mg IV. Chronic HF/oedema: 20–80mg OD oral

Route: IV / Oral

Frequency: Once or twice daily (oral); single dose or infusion (IV)

Max: 600mg/day (oral, resistant oedema). IV infusion: 250mg over 1h if bolus fails

Acute pulmonary oedema: 40–80mg IV over 1–2 min. If no response in 1h: 80mg IV. Resistant oedema: combine with thiazide (metolazone 2.5–5mg). CKD: higher doses needed (40–250mg IV).

Paediatric dose

Dose: 1 mg/kg

Route: IV / Oral

Frequency: Once or twice daily

Max: 40mg

Concentration: 10 mg/ml

Dose adjustments

Renal

Larger doses required in CKD as tubular secretion is reduced. Max effective IV dose may be 250mg in severe CKD.

Hepatic

Use with caution in hepatic cirrhosis — risk of electrolyte disturbance precipitating hepatic encephalopathy.

Paediatric weight-based calculator

Patient weight (kg)

Clinical pearls

In ACUTE pulmonary oedema: IV furosemide acts within 30 min via direct venodilation (before diuresis begins), reducing cardiac preload.
Give IV furosemide at rate not exceeding 4mg/min — rapid infusion causes ototoxicity.
Metolazone sequential nephron blockade: add metolazone 2.5mg 30 min BEFORE furosemide for diuretic resistance — synergistic effect.
Monitor electrolytes every 2–3 days in acute setting. Aim K+ >3.5 mmol/L before digoxin.
In cirrhosis: prefer spironolactone:furosemide ratio 100:40 to maintain potassium balance.

Contraindications

Anuria / hypovolaemia
Severe hypokalaemia or hyponatraemia (correct first)
Sulfonamide hypersensitivity (cross-reactivity — rare)
Addison's disease (relative)

Side effects

Hypokalaemia (most common — supplement K+ and monitor)
Hyponatraemia, hypomagnesaemia
Ototoxicity with high IV doses (especially with aminoglycosides)
Hyperuricaemia and gout
Dehydration, orthostatic hypotension
Hyperglycaemia

Interactions

Aminoglycosides (gentamicin): additive ototoxicity and nephrotoxicity
NSAIDs: reduced diuretic efficacy (prostaglandin antagonism) and renal toxicity
Digoxin: hypokalaemia potentiates digoxin toxicity — maintain K+ >3.5 mmol/L
Lithium: increases lithium levels — monitor levels
ACE inhibitors + furosemide + NSAIDs: triple whammy AKI risk

Monitoring

U&E
creatinine
blood glucose
uric acid
weight
urine output
BP

Reference: BNFc; NICE NG106 Chronic HF; NICE BNF 84. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Furosemide Stress Test (FST) for AKI Progression · AKI

Drugs

Spironolactone · Diuretic

Pathways