What is the recommended oral dose of furosemide (Lasix) for a neonate?

Oral Furosemide Dosing in Neonates

For neonates requiring oral furosemide, start with 0.5–2 mg/kg per dose, administered up to 6 times daily (maximum 10 mg/kg/day) for severe edema, or use 2–5 mg/kg per day divided for stable patients, with the critical caveat that doses exceeding 6 mg/kg/day should never be continued beyond 1 week due to irreversible ototoxicity risk. 1

Initial Dosing Strategy

For acute management of severe edema:

• Begin with 0.5–2 mg/kg per dose orally, administered up to 6 times daily based on edema severity and diuretic response 1
• The absolute maximum daily dose is 10 mg/kg/day, reserved only for extreme circumstances of severe fluid overload 1, 2
• The FDA-approved pediatric dosing starts at 2 mg/kg as a single dose, which may be increased by 1–2 mg/kg increments no sooner than 6–8 hours after the previous dose 3

For stable/maintenance therapy:

• Use 2–5 mg/kg per day orally, typically divided into 1–2 daily doses 1
• Consider combination with a thiazide or potassium-sparing diuretic (preferably amiloride over spironolactone) for enhanced effect 1

Critical Safety Thresholds

The most important safety consideration is ototoxicity:

• Never exceed 6 mg/kg/day for longer than 1 week to prevent permanent hearing loss 1, 2
• High doses (>6 mg/kg/day) carry a 48-fold increased risk of nephrocalcinosis in low birth weight infants 4
• Cumulative doses above 4 mg/kg significantly increase the risk of electrolyte abnormalities, particularly in preterm neonates 5

Mandatory Pre-Administration Assessment

Never administer furosemide if any of the following are present:

• Marked hypovolemia or signs of intravascular volume depletion 1, 2
• Hypotension or poor peripheral perfusion 1
• Anuria (must stop furosemide immediately if this develops) 1
• Severe hyponatremia 1

Before each dose, assess:

• Intravascular volume status (capillary refill time, blood pressure, heart rate) 1, 2
• Urine output and fluid balance 1, 2
• Serum electrolytes (sodium, potassium, calcium, magnesium, bicarbonate, chloride) 1, 5
• Renal function (serum creatinine, estimated GFR) 1

Essential Monitoring During Therapy

Continuous monitoring requirements include:

• Fluid status and urine output (target varies by indication but generally >1 mL/kg/hour) 1, 4
• Electrolytes: hypokalaemia and hyponatraemia are common complications requiring replacement 1, 5
• Blood pressure: watch for hypotension from excessive diuresis 1
• Body weight: daily weights help assess fluid balance 5
• Renal function: elevated serum creatinine occurred in 21% of critically ill neonates receiving furosemide 5

Special Clinical Contexts

For congenital nephrotic syndrome:

• The 2021 ERKNet-ESPN consensus guidelines specifically address this population 1
• Use furosemide cautiously and only with intravascular fluid overload (good perfusion + high blood pressure) 1
• Consider 0.5–2 mg/kg IV or oral bolus at the end of albumin infusions if no marked hypovolemia present 1

For congestive heart failure:

• Start at 1 mg/kg and titrate by 1 mg/kg increments until adequate diuresis 6
• Frequency up to 6 times daily based on edema and diuresis 6
• Use cautiously in dilated cardiomyopathy as acute preload reduction may cause hypotension 6

For premature infants:

• Maximum dose should not exceed 1 mg/kg/day due to increased vulnerability 7
• Half-life is considerably longer (8–27 hours) compared to adults (33–100 minutes), necessitating less frequent dosing 4
• Clearance is significantly reduced at birth and improves with maturation 4

Route Considerations: Oral vs. IV

Oral bioavailability considerations:

• Oral absorption is variable in neonates, particularly in critically ill patients 4, 8
• The Nature Reviews Nephrology guidelines note that oral and IV routes can be used interchangeably at the same mg/kg dose for severe edema management 1
• For acute situations requiring rapid diuresis, IV route is preferred; oral route is appropriate for stable maintenance therapy 1

Common Pitfalls to Avoid

1. Do not use furosemide routinely or prophylactically (e.g., for blood transfusions)—reserve only for symptomatic fluid overload 7

2. Never exceed 6 mg/kg/day for more than 1 week without compelling indication, as permanent hearing loss can occur 1, 2, 7

3. Avoid administering in hypovolemic states—furosemide worsens volume depletion and can precipitate thrombosis 1, 2

4. Do not combine with indomethacin without careful monitoring, as this increases acute renal failure risk 4

5. Monitor for nephrocalcinosis in low birth weight infants receiving cumulative doses >10 mg/kg 4

6. Ensure adequate electrolyte replacement, particularly potassium, as hypokalemia is common 1, 5

Practical Dosing Algorithm

Step 1: Assess volume status

• If hypovolemic, hypotensive, or anuric → DO NOT give furosemide 1, 2
• If euvolemic with fluid overload → proceed to Step 2

Step 2: Determine severity

• Severe edema: Start 0.5–2 mg/kg per dose orally, up to 6 times daily (max 10 mg/kg/day) 1
• Moderate/stable: Start 2–5 mg/kg/day orally divided 1–2 times daily 1

Step 3: Titrate based on response

• Increase by 1–2 mg/kg increments if inadequate diuresis after 6–8 hours 3
• Never exceed 6 mg/kg/day for >1 week 1, 2

Step 4: Monitor and adjust

• Check electrolytes, renal function, and fluid status before each dose adjustment 1, 5
• Consider adding thiazide or amiloride if response inadequate at maximum safe furosemide dose 1