Bumetanide 4 mg Equals Approximately 160 mg of Furosemide (Lasix)
Using the established 1:40 potency ratio, bumetanide 4 mg is equivalent to furosemide 160 mg. 1
Dosing Equivalence
The FDA-approved drug label for bumetanide explicitly states that 1 mg of bumetanide has diuretic potency equivalent to approximately 40 mg of furosemide, establishing a 1:40 conversion ratio 1. This means:
- Bumetanide 1 mg = Furosemide 40 mg
- Bumetanide 4 mg = Furosemide 160 mg
This equivalence ratio is consistently supported across multiple guidelines and research studies 2, 3, 4, 5.
Clinical Validation
Recent clinical research has validated this conversion ratio in real-world practice:
- A 2013 retrospective study in heart failure patients found a potency ratio of 41:1 for intermittent IV dosing and 34:1 overall, closely supporting the standard 40:1 ratio 6
- Multiple controlled studies comparing bumetanide 0.5-2 mg/day with furosemide 20-80 mg/day demonstrated comparable clinical efficacy 4
- Long-term studies confirmed that bumetanide 1 mg produces effects comparable to 40 mg furosemide in edematous patients 5
Important Pharmacokinetic Differences
While the potency is equivalent, bumetanide has a significantly shorter duration of action (4-6 hours) compared to furosemide (6-8 hours) 2, 3. This means:
- Bumetanide 4 mg may require twice-daily dosing to maintain 24-hour diuretic coverage, whereas furosemide 160 mg might be given once or twice daily 3
- The shorter half-life (1-1.5 hours for bumetanide vs longer for furosemide) affects dosing frequency 1, 7
Critical Monitoring Considerations
When converting between these diuretics at equivalent doses, monitor within 1-2 weeks for 2, 3:
- Renal function (serum creatinine, GFR)
- Electrolytes (sodium, potassium, magnesium)
- Volume status (daily weights, signs of dehydration or inadequate diuresis)
- Urine output and clinical response
Common Pitfall to Avoid
Do not assume identical clinical responses despite equivalent potency. Individual patient factors including renal function, volume status, and concurrent medications (especially NSAIDs) can significantly affect diuretic efficacy 2, 3. The conversion ratio provides a starting point, but dose adjustments based on clinical response are frequently necessary 3, 6.
For patients with advanced chronic kidney disease, bumetanide may demonstrate superior efficacy compared to equivalent doses of furosemide 4.