What is the recommended dose of furosemide (Lasix) infusion in adults?

Furosemide Infusion Dosing in Adults

For adult patients requiring furosemide infusion, the recommended initial dose is 40 mg IV bolus followed by a continuous infusion of 10-40 mg per hour, with a maximum infusion rate of 4 mg/minute and a maximum daily dose of 600 mg. 1, 2

Initial Dosing Algorithm

1. Initial IV bolus:

   • Diuretic-naïve patients: 20-40 mg IV bolus given slowly over 1-2 minutes 1
   • Patients already on oral diuretics: At least equal to previous oral dose 2
   • Patients with renal dysfunction or chronic diuretic use: Higher initial doses may be needed 2

2. Continuous infusion initiation:

   • Start at 10-40 mg per hour after initial bolus 3
   • Administer at a rate not exceeding 4 mg/minute 1
   • Ensure solution pH is above 5.5 to prevent precipitation 1

Dose Titration

• Assess response after 1-2 hours
• If inadequate response:
  • Increase dose by 20 mg increments 1
  • Wait at least 2 hours between dose adjustments 1
  • For severe heart failure, doses may be increased up to 160-200 mg per bolus 3

Maximum Dosing

• Maximum single IV bolus dose: 160-200 mg 3
• Maximum daily dose: 600 mg 2, 1
• In refractory cases, higher doses (≥500 mg/day) have been used but require careful monitoring 4

Administration Considerations

• Furosemide is a buffered alkaline solution with pH of about 9 1
• Must be added to compatible solutions:
  • Sodium Chloride Injection USP
  • Lactated Ringer's Injection USP
  • Dextrose (5%) Injection USP
• Do not mix with acidic solutions or medications (e.g., labetalol, ciprofloxacin, amrinone, milrinone) as precipitation may occur 1
• Do not add to running IV lines containing acidic products 1

Monitoring Parameters

• Urine output (target: adequate diuresis, typically >100 mL/hour) 5
• Daily weight
• Electrolytes (particularly potassium, sodium, magnesium)
• Renal function
• Blood pressure (maintain SBP >90 mmHg) 2
• Signs of dehydration or fluid overload

Warning Signs Requiring Dose Adjustment

• Hypotension (SBP <90 mmHg)
• Creatinine increase >50% from baseline or >3.0 mg/dL
• Potassium <3.5 or >5.5 mmol/L
• Signs of dehydration 2
• Tinnitus or hearing impairment (signs of ototoxicity) 1

Special Considerations

• For patients with hepatic cirrhosis and ascites, therapy should be initiated in the hospital with careful monitoring 1
• In patients with severe progressive renal disease, discontinue if increasing azotemia and oliguria occur 1
• For elderly patients, start at the lower end of the dosing range 1
• Consider adding spironolactone to prevent hypokalemia and metabolic alkalosis 3, 1

Alternative Approaches for Diuretic Resistance

1. Sequential nephron blockade:

   • Add thiazide diuretic (e.g., chlorothiazide 500-1000 mg IV) 3
   • Add metolazone 2.5-5 mg PO once or twice daily 3

2. Alternative loop diuretics with equivalent doses:

   • Bumetanide: 1 mg IV bolus then 0.5-2 mg/hour infusion (max 10 mg/day) 3, 2
   • Torsemide: 20 mg IV bolus then 5-20 mg/hour infusion (max 200 mg/day) 3, 2

By following this structured approach to furosemide infusion dosing, clinicians can effectively manage volume overload while minimizing risks of electrolyte imbalances, ototoxicity, and renal dysfunction.