What is the equivalent dose of Lasix (furosemide) for a patient on torsemide?

From the Guidelines

The equivalent dose of Lasix (furosemide) for a patient on torsemide is approximately 2:1, meaning 20 mg of furosemide is equivalent to 10 mg of torsemide. When converting a patient from torsemide to furosemide, it is essential to consider the differences in bioavailability and duration of action between the two medications. According to the 2022 AHA/ACC/HFSA guideline for the management of heart failure 1, torsemide has a higher bioavailability (80-100%) compared to furosemide (50-60%), making torsemide more potent on a milligram-per-milligram basis. Additionally, torsemide has a longer duration of action (12-16 hours) than furosemide (6-8 hours), so when switching to furosemide, patients may require twice-daily dosing instead of once-daily dosing to maintain similar diuretic coverage throughout the day.

Some key points to consider when converting from torsemide to furosemide include:

• The initial daily dose of furosemide is 20-40 mg, while the maximum total daily dose is 600 mg 1
• The duration of action of furosemide is 6-8 hours, which may require more frequent dosing compared to torsemide 1
• Monitoring for fluid status, electrolytes (particularly potassium), and renal function is essential after making this conversion to ensure the patient is receiving appropriate diuretic therapy
• The use of diuretics should be guided by the principles of achieving and maintaining euvolaemia, with the lowest achievable dose, as outlined in the 2012 ESC guidelines for the diagnosis and treatment of acute and chronic heart failure 1

In terms of specific dosing, a patient taking 20 mg of torsemide would need approximately 40 mg of furosemide to achieve similar diuretic effects. However, this conversion should be individualized based on the patient's response to the medication and their underlying clinical condition. It is also important to note that the doses of commonly used diuretics, including furosemide and torsemide, are outlined in the 2012 ESC guidelines 1, which provide practical guidance on the use of diuretics in the treatment of heart failure.

From the Research

Torsemide to Lasix Dose Conversion

To convert a patient from torsemide to Lasix (furosemide), it is essential to understand the potency and pharmacokinetics of both drugs.

• Torsemide is at least twice as potent as furosemide on a weight-for-weight basis 2.
• A dose equivalence of approximately 40 mg oral furosemide:10 mg oral torsemide resulted in similar natriuresis 3.
• However, another study suggested a dose equivalence of approximately 4:1 resulted in similar natriuresis 3.

Key Considerations

When converting from torsemide to furosemide, consider the following:

• The potency difference between the two drugs
• The individual patient's response to diuretic therapy
• The presence of any renal or hepatic impairment
• The need for close monitoring of electrolyte levels and renal function

Clinical Evidence

Clinical trials have shown that torsemide and furosemide have similar efficacy in treating edema and hypertension 2, 4.

• Torsemide may have a longer duration of action and be more effective in patients with renal impairment 4, 5.
• However, the choice of diuretic ultimately depends on individual patient factors and clinical judgment 3, 6.