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Loop Diuretic Pregnancy: Caution — may reduce placental perfusion; avoid in first trimester; used in severe APO in pregnancy under specialist guidance

Furosemide (IV — ICU)

Brand names: Lasix

Adult dose

Dose: Acute pulmonary oedema: 40–80 mg IV slow (over 1–5 min). Refractory oedema: infusion 0–5–5 mg/h. Maximum IV bolus rate: 4 mg/min to reduce ototoxicity risk.
Route: IV slow injection or infusion
Frequency: Bolus PRN or continuous infusion
Max: IV: max rate 4 mg/min. Bolus max 80 mg for standard dose; up to 250 mg in renal failure with careful monitoring
IV has faster onset than oral (20–30 min vs 1–2 h). Alkaline — do not mix in same syringe as acid drugs. Do NOT infuse at >4 mg/min — ototoxicity risk.

Paediatric dose

Dose: 0.5 mg/kg
Route: IV slow over 5 min
Frequency: Every 6–12 hours PRN
Max: 6 mg/kg/day
Concentration: 10 mg/mL mg/ml
Neonates: 0.5–1 mg/kg every 12–24h; avoid use <31 weeks gestation. PDA: furosemide exacerbates PDA — use with caution.

Dose adjustments

Renal

Higher doses required in renal failure (reduced tubular secretion). Up to 250 mg IV in severe renal impairment (administer slowly as ototoxicity risk).

Hepatic

Caution — electrolyte disturbances can precipitate hepatic encephalopathy. Use cautiously and monitor electrolytes.

Paediatric weight-based calculator

Neonates: 0.5–1 mg/kg every 12–24h; avoid use <31 weeks gestation. PDA: furosemide exacerbates PDA — use with caution.

Clinical pearls

  • IV furosemide in APO: onset 20–30 min; initial venodilatory effect (before diuresis) reduces preload
  • DOSE trial: high-dose vs low-dose, bolus vs infusion — high-dose infusion marginally more effective but more adverse effects; current practice varies
  • 'Triple whammy' (furosemide + ACEi + NSAID): high AKI risk — avoid in at-risk patients
  • Ototoxicity: rapid injection (>4 mg/min) and concurrent aminoglycosides are risk factors — always inject slowly

Contraindications

  • Anuria (no response expected)
  • Pre-comatose states in hepatic cirrhosis
  • Hypokalaemia/hyponatraemia (until corrected)

Side effects

  • Hypokalaemia
  • Hyponatraemia
  • Dehydration
  • Ototoxicity (high doses, rapid infusion — especially with aminoglycosides)
  • Hyperuricaemia
  • Hyperglycaemia (mild)
  • Postural hypotension

Interactions

  • Aminoglycosides — additive ototoxicity and nephrotoxicity
  • Digoxin — hypokalaemia increases toxicity
  • NSAIDs — reduce diuretic effect and nephrotoxicity
  • Lithium — increased toxicity
  • ACEi — first-dose hypotension

Monitoring

  • Electrolytes (K+, Na+, Mg2+) — daily in ICU
  • Renal function
  • Fluid balance and weight
  • Blood pressure
  • Urine output

Reference: BNFc; BNF; DOSE Trial (Felker et al, NEJM 2011); ESC Heart Failure Guidelines 2021. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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