IV Furosemide to Bumetanide Dose Conversion
The standard IV dose conversion ratio from furosemide (Lasix) to bumetanide (Bumex) is 40:1, meaning 40 mg of IV furosemide is equivalent to 1 mg of IV bumetanide 1, 2, 3.
Practical Conversion Guidelines
When converting from IV furosemide to IV bumetanide:
- 40 mg IV furosemide = 1 mg IV bumetanide
- 80 mg IV furosemide = 2 mg IV bumetanide
- 160 mg IV furosemide = 4 mg IV bumetanide
Initial Dosing Recommendations
For patients already on loop diuretics 1:
- Convert the total daily oral furosemide dose to IV using 1-2.5 times the home dose
- Then apply the 40:1 conversion ratio to determine bumetanide dose
- Example: Patient on 80 mg oral furosemide daily → 80-200 mg IV furosemide equivalent → 2-5 mg IV bumetanide
For diuretic-naïve patients 2, 3:
- Start with furosemide 20-40 mg IV OR bumetanide 0.5-1 mg IV
- Administer slowly over 1-2 minutes
Administration Details
Bumetanide administration 3:
- Give IV push over 1-2 minutes
- May repeat at 2-3 hour intervals if inadequate response
- Maximum daily dose: 10 mg
Furosemide administration 2:
- Give IV push slowly over 1-2 minutes
- May repeat at 2-hour intervals, increasing by 20 mg increments
- Maximum single bolus dose: 200 mg
Continuous Infusions
If using continuous infusions 1:
- Furosemide: 5-20 mg/hour (maximum 40 mg/hour)
- Bumetanide: 0.5-2 mg/hour (maximum 4 mg/hour)
- This maintains approximately a 40:1 ratio
Evidence Supporting the 40:1 Ratio
The 40:1 conversion ratio is well-established across multiple sources:
- FDA drug labels explicitly support this ratio 2, 3
- ACC/AHA guidelines use this ratio in their dosing tables 1, 4
- Research validation: A 2013 retrospective study in heart failure patients confirmed a 41:1 potency ratio for intermittent IV dosing and 34:1 for all patients, supporting the standard 40:1 clinical conversion 5
- Pharmacologic studies demonstrate bumetanide is approximately 40-50 times more potent than furosemide on a milligram basis 6, 7
Important Clinical Considerations
Bumetanide may offer advantages 5, 8:
- Higher oral bioavailability than furosemide
- More predictable absorption
- May produce greater urine output in some patients
- Potentially less ototoxicity than furosemide 6
Common pitfall: Some older studies suggested ratios ranging from 25:1 to 50:1 9, 7, but the 40:1 ratio remains the standard for clinical practice and is endorsed by current guidelines and FDA labeling.
Monitoring requirements 1:
- Check electrolytes (especially potassium and magnesium) daily during IV therapy
- Monitor renal function (creatinine, BUN)
- Track daily weights and urine output
- Both drugs can cause hypokalemia, hypomagnesemia, and volume depletion
Renal dysfunction: In patients with chronic renal insufficiency, bumetanide may require higher doses relative to furosemide (ratio closer to 34:1), though the 40:1 ratio remains a reasonable starting point 10.