What is the dose equivalent of bumetanide (Bumex) to furosemide in a chronic heart‑failure patient with elevated BNP (535 pg/mL) and new lower‑extremity edema who is receiving a small amount of intravenous fluid for CT contrast?

Bumetanide to Furosemide Dose Equivalence

The established dose equivalence ratio is 1 mg bumetanide equals 40 mg furosemide, meaning your patient's bumetanide dose should be converted by dividing by 40 to determine the equivalent furosemide dose. 1, 2, 3

Core Conversion Ratio

• 1 mg bumetanide = 40 mg furosemide is the FDA-approved and guideline-supported conversion ratio 1, 2, 3
• This 1:40 potency ratio has been validated in multiple clinical studies, including a 2013 retrospective evaluation in heart failure patients that confirmed a 41:1 ratio for intermittent IV dosing and 34:1 for all heart failure patients, supporting the standard 40:1 equivalence 3
• Pharmacological studies consistently demonstrate bumetanide is approximately 40-fold more potent than furosemide, with the exception of potassium excretion where the difference is less pronounced 2

Practical Conversion Examples for Your Patient

For a chronic heart failure patient with elevated BNP and new lower-extremity edema:

• If on bumetanide 1 mg daily → convert to furosemide 40 mg daily 1, 2
• If on bumetanide 2 mg daily → convert to furosemide 80 mg daily 1, 2
• If on bumetanide 0.5 mg daily → convert to furosemide 20 mg daily 1, 2

Critical Pharmacokinetic Differences to Consider

Bumetanide has a significantly shorter duration of action (4–6 hours) compared to furosemide (6–8 hours), which often necessitates twice-daily dosing rather than once-daily. 4, 1

• Peak diuretic effect occurs within 15–30 minutes for IV bumetanide versus 30–60 minutes for IV furosemide 1, 2
• Oral bumetanide reaches peak effect at approximately 75 minutes, similar to furosemide 5
• The shorter half-life of bumetanide (1–1.5 hours) versus furosemide means patients may require split dosing to maintain 24-hour diuretic coverage 4, 1

Route-Specific Adjustments

When converting from IV to oral, recognize that IV bumetanide is approximately 3 times more potent than oral bumetanide due to bioavailability differences. 5

• For both drugs, the IV dose is approximately three times as potent as the oral preparation 5
• If your patient was on IV bumetanide 1 mg and you're switching to oral furosemide, consider that IV bumetanide 1 mg ≈ oral bumetanide 3 mg ≈ oral furosemide 120 mg 5

Monitoring After Conversion

Check daily weights targeting 0.5–1.0 kg loss per day, and monitor electrolytes and renal function within 1–2 weeks after conversion. 6, 4

• Monitor urine output, targeting >0.5 mL/kg/hour 6, 7
• Check serum sodium, potassium, and creatinine within 24–48 hours, then every 3–7 days during active titration 6, 4
• Assess for signs of volume depletion (hypotension, tachycardia, decreased skin turgor) or inadequate diuresis (persistent edema, weight gain) 6, 4

Special Consideration for Your Patient Context

In a patient receiving IV fluids for CT contrast, delay diuretic administration until systolic blood pressure is ≥90–100 mmHg and ensure adequate intravascular volume before initiating or converting diuretics. 8, 7

• The initial IV dose for patients already on chronic diuretics must be at least equal to (or greater than) their home oral dose equivalence 8, 7
• For a patient with BNP 535 pg/mL and new edema, if previously on bumetanide 1 mg daily, start furosemide 40 mg IV (or higher if inadequate response) 8, 6
• Avoid administering furosemide if marked hypovolemia, severe hyponatremia (sodium <120–125 mmol/L), or anuria is present 8, 7

Common Pitfall to Avoid

Do not underdose when converting from bumetanide to furosemide in patients with chronic heart failure and active congestion—the equivalent dose is the minimum starting point, not the target dose. 8, 6

• Patients with elevated BNP and new edema often require doses higher than their baseline equivalence to achieve adequate decongestion 8, 6
• If inadequate diuresis occurs after 24–48 hours at equivalent dosing, increase furosemide by 20–40 mg increments rather than assuming the conversion ratio is incorrect 8, 6
• Consider adding spironolactone 25–50 mg daily for sequential nephron blockade if furosemide doses exceed 80–160 mg/day without adequate response 8, 6