Loop diuretic
Furosemide
Inhibits the Na-K-2Cl co-transporter in the thick ascending limb, producing potent natriuresis and diuresis with loss of potassium, magnesium and calcium.
Brands
Lasix · Frusenex
Adult dosing
Maximum Commonly 160 mg/day orally; specialist regimens go higher| Indication | Dose | Route | Frequency |
|---|---|---|---|
| Acute pulmonary oedema | 40-80 mgGive at least the usual oral dose intravenously in established users | IV slow bolus | Repeat after 30-60 minutes by response |
| Chronic heart failure congestion | 20-80 mgMax Usually 160 mg/day; higher only under specialist review | Oral | Once or twice daily (avoid late evening) |
| Diuretic resistance | 5-10 mg/hour | IV infusion | Continuous with electrolyte monitoring |
Weight-based: Children: mg/kg. Adults: titrate to weight change and congestion, not a fixed number.
Older adults: Start at the lower end; falls, incontinence and hyponatraemia are the usual harms.
Paediatric dosing
Always confirm the weight and the local paediatric formulary| Indication | Dose | Route | Frequency |
|---|---|---|---|
| Oedema, children | 0.5-2 mg/kg/doseMax 6 mg/kg/day | Oral or IV | Every 8-24 hours |
| Neonate | 0.5-1 mg/kg/doseLonger half-life — extend the interval | IV | Every 24 hours |
Renal adjustment
Move the slider to the patient's eGFRUsual dose
- eGFR ≥ 30Usual dose
- eGFR 15-29Higher doses are needed to reach the tubular site — titrate upward
- eGFR < 15Large doses may be required; assess for dialysis need instead of escalating blindly
Hepatic adjustment
- Cirrhosis with ascitesCombine with spironolactone; watch for encephalopathy and hypokalaemia
Practical notes
The things that go wrong at the bedside- Oral bioavailability is 50% and erratic in gut oedema — the intravenous dose is roughly half the oral dose.
- Track daily weight, urea, creatinine, sodium and potassium during active decongestion.
DrZep structured dosing table (demo dataset, formulary-aligned) · DrZep. Confirm every dose against your local formulary and the patient's weight, renal function and comorbidities.
Indications
- Acute decompensated heart failure and pulmonary oedema
- Chronic congestion in heart failure
- Oedema in nephrotic syndrome and cirrhosis
- Hypercalcaemia (with volume repletion)
- Fluid overload in chronic kidney disease
Dosing summary
- Acute pulmonary oedema
- 20-40 mg intravenously; in patients already on furosemide give 1-2.5× the usual oral dose intravenously
- Chronic oral
- 20-80 mg daily in 1-2 doses, titrated to weight and symptoms
- Infusion (refractory)
- 5-20 mg/h after a loading dose, with electrolyte monitoring
- Renal impairment
- Higher doses are needed to reach the tubular site of action
Organ adjustment
Renal
- eGFR 20-50
- Usual doses; may need escalation
- eGFR < 20
- High doses often required; avoid rapid IV push above 4 mg/min (ototoxicity)
- Anuric AKI
- Do not use to 'convert' oliguric AKI — no benefit on outcomes
Hepatic
- Cirrhosis with ascites
- Usually combined with spironolactone in a 40:100 mg ratio; watch for encephalopathy and hyponatraemia
Monitoring
- 1Daily weight and fluid balance in acute care
- 2Urea, electrolytes and creatinine within 24-72 h of a dose change
- 3Blood pressure and symptoms of hypovolaemia
- 4Potassium and magnesium replacement as needed
Contraindications & cautions
Do not use / use with care
- Anuria unresponsive to a trial dose
- Severe untreated hypokalaemia or hyponatraemia
- Hepatic coma
- Sulfonamide-type hypersensitivity (rare cross-reactivity)
Pregnancy & lactation
- Pregnancy
- Use only for a clear maternal indication (e.g. heart failure); not for gestational oedema or hypertension.
- Lactation
- Compatible but may suppress lactation.
Interactions
- AminoglycosidesAdditive ototoxicity and nephrotoxicitymajor
- LithiumReduced clearance and lithium toxicitymajor
- DigoxinHypokalaemia potentiating digoxin toxicitymajor
- NSAIDsBlunted diuresis and increased AKI riskmoderate
- QT-prolonging drugsElectrolyte-mediated arrhythmia riskmoderate
Adverse effects
Common
- Polyuria
- Postural hypotension
- Hypokalaemia
- Hypomagnesaemia
- Hyperuricaemia and gout
Serious
- Acute kidney injury from over-diuresis
- Severe hyponatraemia
- Ototoxicity with rapid high-dose IV administration
- Metabolic alkalosis
- Rare bullous and Stevens-Johnson reactions
Toxicity & overdose
Recognise and treat
- Over-diuresis leads to hypovolaemia, prerenal AKI and profound electrolyte disturbance — hold the drug, replace volume cautiously and correct electrolytes
Alternatives
- Bumetanide or torsemide (better oral bioavailability in gut oedema)
- Thiazide added for diuretic resistance (sequential nephron blockade)
- MRA and SGLT2 inhibitor for chronic decongestion
- Ultrafiltration in refractory overload
Linked diseases & guidelines
ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure
Four-pillar therapy for HFrEF, SGLT2 inhibitors across the ejection-fraction spectrum, congestion management.
European Society of CardiologyEurope2023
KDIGO Clinical Practice Guideline for Acute Kidney Injury
AKI definition and staging, nephrotoxin stewardship and indications for renal replacement therapy.
KDIGOGlobal2012
Demo monograph for educational use. Always confirm dose, route and interactions against your national formulary and the product label before prescribing.
Demo content. Educational decision support only. Verify every dose, citation and recommendation against your national formulary and the primary source before clinical use.