Equivalent Dosing of Furosemide, Bumetanide, and Torsemide
The equivalent dosing ratio of furosemide to bumetanide to torsemide is 40:1:10, meaning 40 mg of furosemide equals 1 mg of bumetanide equals 10 mg of torsemide. 1, 2, 3
Pharmacological Properties and Equivalence
- Bumetanide is a potent loop diuretic with a diuretic potency approximately 40 times that of furosemide (1 mg bumetanide ≈ 40 mg furosemide) 2
- Torsemide has a potency ratio of approximately 4:1 compared to furosemide (10 mg torsemide ≈ 40 mg furosemide) 3
- All three medications work through the same mechanism: inhibition of the Na+/K+/2Cl- cotransport in the thick ascending limb of the loop of Henle 4
Pharmacokinetic Differences
Duration of Action
- Bumetanide has a short duration of action (4-6 hours) and elimination half-life of 1-1.5 hours 1, 2
- Furosemide has an intermediate duration of action with variable bioavailability 3
- Torsemide has a longer elimination half-life (3-4 hours) compared to both bumetanide and furosemide 4, 5
Bioavailability
- Bumetanide has high bioavailability (>80%) 2
- Torsemide also has high bioavailability (>80%) 4, 5
- Furosemide has more variable and generally lower bioavailability compared to the other two agents 3
Clinical Applications and Dosing Considerations
- For initial treatment in acute heart failure, the recommended starting dose is 20-40 mg IV furosemide (or equivalent: 0.5-1 mg bumetanide or 10-20 mg torsemide) 6
- For patients on chronic diuretic therapy, the initial IV dose should be at least equivalent to their oral dose 6
- Maximum daily dose of bumetanide should not exceed 10 mg 1
Special Considerations
- Despite theoretical pharmacokinetic advantages of torsemide over furosemide (longer half-life, better bioavailability), recent research shows no significant clinical outcome differences between the two medications 3
- When higher doses of torsemide are used (compared to equivalent furosemide doses), greater neurohormonal activation and kidney dysfunction may occur, offsetting the natriuretic benefits 3
- Bumetanide may show a more dose-dependent diuretic effect in patients recovering from acute renal failure 7
Common Pitfalls and Caveats
- Clinicians often use a 2:1 dose equivalence conversion between furosemide and torsemide, but research suggests a 4:1 ratio results in similar natriuresis 3
- When switching between diuretics, careful monitoring of electrolytes, renal function, and clinical response is essential 1
- All loop diuretics can cause similar adverse effects including electrolyte disturbances (particularly hypokalemia), hyperuricemia, and activation of the renin-angiotensin-aldosterone system 4, 8
- Combination therapy with thiazide diuretics may be considered in cases of diuretic resistance rather than exceeding maximum recommended doses of loop diuretics 6, 1