What is the recommended dosage of Lasix (furosemide)?

Furosemide Dosage Recommendations

Initial Dosing by Clinical Indication

For edema, start with furosemide 20-80 mg as a single oral dose, with 40 mg being the most common initial dose for most adults with fluid overload. 1, 2

Heart Failure with Acute Pulmonary Edema

• Administer 20-40 mg IV bolus over 1-2 minutes as the initial dose 1
• For patients already taking >40 mg daily at home, start with 80 mg IV instead 1
• Systolic blood pressure must be ≥90-100 mmHg before administration 1
• Do not give furosemide to hypotensive patients—it will worsen tissue perfusion and precipitate cardiogenic shock 1

Cirrhosis with Ascites

• Start with furosemide 40 mg orally combined with spironolactone 100 mg as a single morning dose 1, 3, 4
• Maintain the 100:40 mg spironolactone-to-furosemide ratio throughout treatment 3, 4
• Oral route is preferred over IV to avoid acute GFR reduction 1
• Maximum dose is 160 mg/day; exceeding this indicates diuretic resistance requiring paracentesis 1, 4

Nephrotic Syndrome

• In adults with severe edema, start furosemide 0.5-2 mg/kg per dose IV or orally, up to 6 times daily (maximum 10 mg/kg/day) 1, 4
• After albumin infusions, give 0.5-2 mg/kg IV at the end of infusion if no marked hypovolemia or hyponatremia 1, 4

Pediatric Dosing

• Initial dose is 2 mg/kg body weight as a single oral dose 2
• May increase by 1-2 mg/kg no sooner than 6-8 hours after previous dose 2
• Doses >6 mg/kg body weight are not recommended 2

Dose Escalation Strategy

If initial dose produces inadequate diuresis, increase by 20-40 mg increments no sooner than 6-8 hours after the previous dose 1, 2

Maximum Dosing Limits

• In acute heart failure: Do not exceed 100 mg in first 6 hours or 240 mg in first 24 hours 1
• In cirrhosis: Maximum 160 mg/day 1, 4
• In severe edematous states: May carefully titrate up to 600 mg/day 2
• For refractory cardiac failure, doses up to 500 mg per dose have been used safely when given by infusion over 4 hours 1, 5

High-Dose Administration Precautions

• Doses ≥250 mg must be given by infusion over 4 hours to prevent ototoxicity 1
• Infusions should be administered over 5-30 minutes for doses <250 mg 1, 4
• High doses (>6 mg/kg/day) should not be given for periods longer than 1 week 1

Dosing Frequency

Give furosemide as a single morning dose for chronic management to improve adherence and reduce nocturia 1

• In acute settings, doses may be repeated every 6-8 hours 2
• Avoid evening doses—they cause nocturia and poor adherence without improving outcomes 1
• For pediatric nephrotic syndrome, may dose up to 6 times daily 1, 4

Continuous Infusion Alternative

For patients requiring ≥120 mg or with inadequate response to bolus dosing, consider continuous infusion at 5-10 mg/hour (maximum rate 4 mg/min) 1

Absolute Contraindications to Dosing

Stop or do not initiate furosemide if any of the following are present: 1, 4

• Anuria
• Marked hypovolemia
• Systolic blood pressure <90 mmHg without circulatory support
• Severe hyponatremia (serum sodium <120-125 mmol/L)
• Severe hypokalemia (<3 mmol/L)
• Progressive renal failure or acute kidney injury (context-dependent)

Critical Monitoring Requirements

Check electrolytes (sodium, potassium) and renal function within 3-7 days of initiation, then weekly during dose titration 1, 3

• Monitor daily weights targeting 0.5 kg/day loss without peripheral edema, or 1.0 kg/day with peripheral edema 1, 4
• Exceeding these weight loss targets increases risk of intravascular volume depletion and renal failure 1
• Place bladder catheter in acute settings to monitor urine output hourly 1
• Monitor blood pressure every 15-30 minutes in first 2 hours after high-dose administration 1

Diuretic Resistance Management

If inadequate response after 24-48 hours at appropriate doses, add combination therapy rather than escalating furosemide alone 1

• Add hydrochlorothiazide 25 mg orally OR spironolactone 25-50 mg orally 1, 3
• In cirrhosis specifically, maintain spironolactone from the beginning 1, 4
• Consider continuous infusion instead of bolus dosing 1

Special Populations

Geriatric Patients

• Start at the low end of the dosing range (20 mg) 2
• Titrate cautiously with close monitoring 2

Renal Impairment

• Higher doses may be required to achieve therapeutic effect 1
• In end-stage renal disease on hemodialysis, doses of 250-2,000 mg daily have been used safely 6, 7
• Monitor for progressive loss of response over time due to declining renal function 7

Common Pitfalls to Avoid

• Never use furosemide expecting it to improve hemodynamics in hypotensive patients—it causes further volume depletion 1
• Do not use furosemide as monotherapy in acute pulmonary edema; start IV nitroglycerin concurrently 1
• In cirrhosis, exceeding 160 mg/day signals need for paracentesis, not further dose escalation 1, 4
• Gut wall edema in heart failure reduces oral bioavailability; IV route is more reliable in acute settings 1
• First dose produces greatest effect; subsequent doses show up to 25% less effect at same concentration 1