What IV bumetanide (Bumex) dose is equivalent to 80 mg IV furosemide (Lasix)?

IV Bumetanide Equivalent to 80 mg IV Furosemide

The equivalent IV bumetanide dose for 80 mg IV furosemide is 2 mg IV bumetanide, based on the established 40:1 potency ratio. 1

Established Dosing Equivalence

The FDA-approved bumetanide label explicitly states that "1 mg bumetanide has a diuretic potency equivalent to approximately 40 mg furosemide." 1 This 40:1 ratio is consistently supported across multiple guidelines and research studies. 2, 3, 4

For 80 mg IV furosemide, the calculation is straightforward:

• 80 mg furosemide ÷ 40 = 2 mg bumetanide IV 1

Guideline-Based Dosing Recommendations

The ACC/AHA guidelines provide clear dosing parameters for IV bumetanide in severe heart failure, listing an initial dose of 1.0 mg with a maximum single dose of 4-8 mg. 2 Therefore, 2 mg bumetanide falls well within the safe and effective dosing range for acute management.

For patients hospitalized with acute heart failure who are already on chronic oral diuretics, guidelines recommend starting IV loop diuretics at at least twice the daily home oral dose equivalent. 2, 3 If a patient was taking furosemide 40 mg daily at home, the appropriate acute IV dose would be 80 mg furosemide (or 2 mg bumetanide equivalent). 2

Important Pharmacokinetic Differences

While the potency ratio is 40:1, bumetanide has a significantly shorter duration of action (4-6 hours) compared to furosemide (6-8 hours). 3, 1 This shorter half-life (1-1.5 hours for bumetanide) means that:

• Bumetanide may require more frequent dosing to maintain 24-hour diuretic coverage 3
• Peak diuretic effect occurs within 15-30 minutes after IV administration for both drugs 1
• The diuretic response returns to baseline by 3.5 hours with IV administration 5

Critical Monitoring Requirements

When administering 2 mg IV bumetanide (equivalent to 80 mg IV furosemide), monitor closely for:

• Electrolyte depletion: Check potassium, magnesium, sodium, and chloride within 24-48 hours 2, 3
• Renal function: Monitor serum creatinine and blood urea nitrogen, as excessive diuresis can impair renal function 2
• Volume status: Assess for signs of volume depletion (hypotension, tachycardia) versus inadequate diuresis (persistent edema, dyspnea) 3
• Daily weights: Target 0.5-1.0 kg loss per day 3
• Urine output: Expect diuresis to begin within minutes and peak within 15-30 minutes 1

Common Pitfalls to Avoid

Do not underdose when converting from furosemide to bumetanide. The 40:1 ratio is well-established, and using a lower conversion ratio (such as 20:1 or 30:1) will result in inadequate diuresis. 1, 4

Avoid administering bumetanide when:

• Systolic blood pressure is <90-100 mmHg 3
• Severe hyponatremia is present (serum sodium <120-125 mmol/L) 3
• Marked hypovolemia or anuria exists 3

Consider potassium supplementation or aldosterone antagonist therapy (spironolactone 25-50 mg daily) from the start, as loop diuretics cause significant potassium and magnesium wasting. 2, 3 Magnesium depletion must be corrected before potassium repletion will be effective. 3

Managing Inadequate Response

If 2 mg IV bumetanide does not produce adequate diuresis within 24-48 hours:

• Increase bumetanide dose by 1-2 mg increments up to a maximum of 8-10 mg per dose 2, 3
• Consider adding a thiazide diuretic (hydrochlorothiazide 25 mg or metolazone 2.5 mg) for sequential nephron blockade rather than exceeding maximum loop diuretic doses 2, 3
• Evaluate for high dietary sodium intake, which can blunt diuretic response 3
• Consider continuous IV infusion (1 mg IV load then 0.5-2 mg/hour) rather than bolus dosing if resistance develops 2