Article written and medically reviewed by Dr. Elena M. Richardson, PharmD, BCPS – Board Certified Pharmacotherapy Specialist. Last updated: November 17, 2025
What is Lasix (Furosemide) Used For?
Lasix (furosemide) is a high-ceiling loop diuretic indicated for:
- Edema associated with congestive heart failure (CHF), cirrhosis of the liver, and renal disease including nephrotic syndrome
- Acute pulmonary edema (IV administration)
- Hypertension (alone or in combination with other antihypertensives)
- Hypercalcemia (off-label)
- Acute kidney injury with volume overload
Dosage and Treatment Regimens (2025 ACC/AHA & KDIGO Guidelines)
Oral Furosemide – Standard Adult Dosing
| Indication | Initial Dose | Maintenance | Maximum Daily Dose |
|---|---|---|---|
| Edema (mild-moderate) | 20–40 mg once daily | 20–80 mg/day | 600 mg |
| Edema (severe/refractory) | 80–160 mg/day divided | Titrate by 20–40 mg increments | 600 mg |
| Hypertension | 40 mg twice daily | 40–80 mg/day divided | 80 mg |
| Acute pulmonary edema (with IV) | 40 mg IV bolus | Follow with infusion if needed | — |
IV to Oral Conversion Ratio
| IV Dose | Equivalent Oral Dose |
|---|---|
| 20 mg IV | 40 mg oral |
| 40 mg IV | 80 mg oral |
| 80 mg IV | 160 mg oral |
Pediatric Dosing
| Route | Dose | Frequency |
|---|---|---|
| Oral/IV | 1–2 mg/kg/dose | Once or twice daily |
| Maximum | 6 mg/kg/day | — |
Comparative Table: Loop Diuretics (2025 Data)
| Drug | Bioavailability | Duration of Action | Potency vs Furosemide | Ototoxicity Risk |
|---|---|---|---|---|
| Furosemide (Lasix) | 50–60 % | 6–8 hours | 1x (reference) | Moderate |
| Bumetanide (Bumex) | 80–100 % | 4–6 hours | 40x | Higher |
| Torsemide (Demadex) | 80–100 % | 12–16 hours | 2–4x | Lower |
| Ethacrynic acid | ~100 % | 6–12 hours | ~1x | Highest |
Mechanism of Action
Furosemide inhibits the Na⁺-K⁺-2Cl⁻ cotransporter in the thick ascending limb of the loop of Henle, blocking reabsorption of approximately 20–25 % of filtered sodium, resulting in profound natriuresis and diuresis.
Side Effects & Monitoring Requirements (2025)
Common: hypokalemia, hyponatremia, hypomagnesemia, dehydration, orthostatic hypotension, increased uric acid.
Serious: ototoxicity (dose-related, especially >240 mg IV rapid), acute kidney injury, severe hypokalemia-induced arrhythmias.
Official Sources
- FDA Prescribing Information (2024): FDA Lasix Label
- EMA Summary of Product Characteristics: EMA Lasix SmPC
- PubMed – DOSE Trial (furosemide in acute decompensated HF): PubMed 36041399
Real Patient Reviews (2024–2025)
“Leg swelling from heart failure disappeared within 3 days. Doctor monitors potassium monthly – no issues.”
“40 mg every morning keeps my blood pressure 130/80 and no more ankle swelling.”
“Works great for fluid, but I have to take potassium supplement. Worth it.”
“After liver cirrhosis diagnosis, 20 mg daily removed 15 lbs of fluid in a week.”
“Effective, but makes me urinate a lot first few hours. Take it early.”
Frequently Asked Questions (FAQ)
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