Loop Diuretic
Pregnancy: Caution — avoid in first trimester; use in second/third trimester only if essential
Furosemide
Brand names: Lasix
Adult dose
Dose: 20–80 mg
Route: Oral / IV / IM
Frequency: Once or twice daily
Max: 600 mg/day (severe cases under specialist care)
Oedema/heart failure: 20–40 mg once daily initially. IV: 20–40 mg slow IV injection (1 mg/min). High-dose infusion for refractory fluid overload. Electrolyte replacement often needed.
Paediatric dose
Dose: 0.5–2 mg/kg
Route: Oral / IV
Frequency: Once or twice daily
Max: 6 mg/kg/day
0.5–2 mg/kg/dose. Oral for chronic use; IV for acute management.
Dose adjustments
Renal
Higher doses may be needed in renal impairment to achieve diuretic response. Avoid in anuric acute renal failure.
Hepatic
Caution in hepatic cirrhosis — hypokalaemia may precipitate hepatic encephalopathy. Start at low dose with potassium monitoring.
Paediatric weight-based calculator
0.5–2 mg/kg/dose. Oral for chronic use; IV for acute management.
Clinical pearls
- Ototoxicity risk with rapid IV injection — give slowly (max 4 mg/min)
- In severe heart failure, consider continuous IV infusion over repeated boluses
- Monitor electrolytes regularly — replace potassium as needed; consider potassium-sparing diuretic combination
Contraindications
- Anuria (except to test renal responsiveness)
- Addison's disease
- Electrolyte depletion (until corrected)
- Pre-comatose liver failure
Side effects
- Hypokalaemia
- Hyponatraemia
- Hypomagnessaemia
- Dehydration/hypovolaemia
- Ototoxicity (high IV doses)
- Hyperuricaemia/gout
- Hyperglycaemia
- Postural hypotension
Interactions
- Digoxin (hypokalaemia increases toxicity risk)
- ACE inhibitors/ARBs (excessive hypotension — 'first-dose' effect)
- NSAIDs (reduce diuretic effect + risk of AKI)
- Aminoglycosides (additive ototoxicity)
- Lithium (toxicity — avoid)
Monitoring
- U&E (especially potassium) before and regularly during treatment
- Fluid balance
- Weight daily in fluid overload
- Blood pressure
Reference: BNFc; BNF 90; NICE NG106 (Chronic Heart Failure); BNFc. Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.
Drugs