Converting Oral Furosemide 20 mg to Bumetanide
The equivalent dose of oral Bumex (bumetanide) for oral Furosemide (Lasix) 20 mg is 0.5 mg, based on the established potency ratio of 1:40. 1, 2, 3
Conversion Rationale
- Bumetanide is approximately 40 times more potent than furosemide on a milligram-to-milligram basis 1, 4
- This means:
- 0.5 mg bumetanide ≈ 20 mg furosemide
- 1 mg bumetanide ≈ 40 mg furosemide
Pharmacological Comparison
Similarities
- Both are loop diuretics that act primarily on the ascending limb of the loop of Henle 1, 2
- Both have rapid onset of action with similar pharmacokinetic profiles 2
- Both are effective in treating fluid retention in heart failure, hepatic disease, and renal disease 3
Differences
- Bumetanide has a more complete oral absorption compared to furosemide 2
- Bumetanide has a shorter duration of action (3-6 hours) 3
- Bumetanide may have a lower risk of ototoxicity compared to furosemide 4
Dosing Considerations
According to the American College of Cardiology guidelines, the recommended dosing parameters are 5:
| Drug | Initial Daily Dose | Maximum Total Daily Dose | Duration of Action |
|---|---|---|---|
| Bumetanide | 0.5 to 1.0 mg once or twice | 10 mg | 4 to 6 hours |
| Furosemide | 20 to 40 mg once or twice | 600 mg | 6 to 8 hours |
Clinical Monitoring After Conversion
- Monitor for diuretic response (urine output, weight changes)
- Watch for electrolyte disturbances, particularly hypokalemia and hypochloremia, which may be more common with bumetanide 4
- Monitor renal function, as excessive diuresis can lead to prerenal azotemia 2
- Assess for signs of dehydration or hypovolemia 6
Important Considerations
- Bumetanide has a more rapid onset of action, with peak plasma levels achieved approximately 30 minutes after oral administration 2
- The half-life of bumetanide is 1.2-1.5 hours, which is shorter than furosemide 2
- For patients with renal impairment, higher doses of bumetanide may be required (up to 15 mg/day), but the standard conversion ratio still applies for initial dosing 3
Potential Pitfalls
- Avoid concurrent use of NSAIDs as they can reduce diuretic effectiveness 6
- Be cautious with high doses in patients with hearing impairment, although bumetanide may have less ototoxicity than furosemide 4
- Monitor for muscle cramps, which can occur with bumetanide, particularly in patients with renal disease 3
When switching between these diuretics, start with the equivalent dose and adjust based on clinical response, always using the lowest effective dose to maintain euvolemia while minimizing adverse effects.