What is the conversion ratio from Torsemide to Furosemide (Lasix)?

From the Guidelines

The conversion ratio from torsemide to furosemide (Lasix) is approximately 1:4, meaning 10 mg of torsemide is equivalent to 40 mg of furosemide. When switching a patient from furosemide to torsemide, divide the furosemide dose by 4 to get the appropriate torsemide dose. Conversely, when changing from torsemide to furosemide, multiply the torsemide dose by 4. For example, a patient taking 20 mg of torsemide would need 80 mg of furosemide for equivalent diuretic effect. This conversion ratio is based on the relative potency of these loop diuretics, as torsemide has greater bioavailability and longer half-life compared to furosemide, as mentioned in the study 1.

Key Points to Consider

• The conversion ratio is crucial to prevent complications such as hypokalemia or hyperkalemia, and to maintain adequate serum potassium levels, as discussed in the guidelines 1.
• Monitor the patient closely for changes in diuretic response, electrolyte levels (particularly potassium), and renal function, as individual responses may vary.
• The study 1 suggests that torsemide is used at a quarter of the dose of furosemide, which supports the 1:4 conversion ratio.
• Another study 1 provides diuretic dosages in patients with heart failure, but the most recent and relevant guideline for the conversion ratio is found in 1.

Clinical Application

• When making this conversion, it is essential to consider the patient's underlying condition, such as liver cirrhosis or heart failure, and adjust the dose accordingly.
• The patient's response to the conversion should be closely monitored, and adjustments made as necessary to prevent complications and maintain optimal diuretic effect.

From the Research

Torsemide to Furosemide Conversion

• The conversion ratio from Torsemide to Furosemide is approximately 1:4 to 1:2.5, with 10 mg of oral torsemide being equivalent to 40 mg of oral furosemide 2.
• However, the optimal conversion ratio may vary depending on the individual patient's response and the specific clinical context.
• A study found that a dose equivalence of approximately 4:1 resulted in similar natriuresis between torsemide and furosemide 2.
• Another study suggested that torsemide 20mg increases plasma renin levels, angiotensin II activity, and urinary dopamine and prostaglandin E excretion, but lower doses of 2.5 to 5 mg/day do not have a significant effect on these parameters 3.

Clinical Implications

• The choice between torsemide and furosemide should be based on individual patient characteristics, such as renal function, electrolyte balance, and response to treatment 4.
• Torsemide may be associated with a slightly lower risk of a composite of all-cause mortality or heart failure hospitalization and urgent visits with intravenous diuretics, but a slightly higher risk of acute kidney injury compared to furosemide 4.
• Clinicians should carefully monitor patients for signs of acute kidney injury, hypovolemia, and hypokalemia when initiating or converting between torsemide and furosemide 4.

Pharmacological Properties

• Torsemide produces a more prolonged water and electrolyte excretion than equipotent diuretic doses of furosemide, but does not increase kaliuresis to the same extent 3.
• Torsemide has a longer duration of action compared to furosemide, but the kidney bioavailability of torsemide is significantly less than that of furosemide 2.