What is the intravenous (IV) equivalent dose of Lasix (furosemide) for a patient on Torsemide (torsemide) 5 mg?

Torsemide to Furosemide IV Conversion

The intravenous (IV) equivalent dose of Lasix (furosemide) for a patient on Torsemide (torsemide) 5 mg is 10-20 mg. 1

Conversion Ratios and Equivalence

• According to European Society of Cardiology guidelines, torsemide 10-20 mg is equivalent to furosemide 20-40 mg when administered intravenously 1
• Therefore, torsemide 5 mg would be approximately equivalent to furosemide 10-20 mg IV 1
• Torsemide has higher bioavailability (>80%) compared to furosemide and a longer elimination half-life (3-4 hours vs 1-2 hours for furosemide) 2

Pharmacological Considerations

• Torsemide belongs to the pyridine-sulfonylurea class of loop diuretics with the same primary mechanism of action as furosemide (blocking sodium/potassium/chloride cotransport in the thick ascending limb of the loop of Henle) 2, 3
• When converting from torsemide to furosemide IV, consider that torsemide has more consistent absorption and longer duration of action 3
• Torsemide might show a better dose-dependent diuretic effect in certain patients, particularly those with acute renal failure 4

Administration Guidelines

• For acute heart failure, the recommended initial IV furosemide dose is 20-40 mg as a bolus 1
• When converting from torsemide to furosemide, patients should be monitored frequently in the initial phase to assess urine output and clinical response 1
• Total furosemide dose should remain <100 mg in the first 6 hours and <240 mg during the first 24 hours 1

Monitoring After Conversion

• After converting from torsemide to furosemide IV, monitor:
  • Urine output (placement of a bladder catheter may be desirable) 1
  • Signs of volume status and congestion 5
  • Serum electrolytes, particularly potassium and sodium 1, 5
  • Blood pressure (watch for hypotension) 1

Potential Adverse Effects

• Common adverse effects to monitor after conversion include:
  • Hypokalaemia, hyponatraemia, hyperuricaemia 1
  • Hypovolaemia and dehydration 1
  • Neurohormonal activation 1
  • Increased risk of hypotension, especially if the patient is on ACE inhibitors or ARBs 1

Special Considerations

• In patients with renal dysfunction, furosemide doses may need to be higher to achieve the same diuretic effect 1
• For patients with diuretic resistance, consider combination therapy with thiazide diuretics rather than extremely high doses of loop diuretics 1

Remember that individual patient response may vary, and the dose should be adjusted based on clinical response and hemodynamic status.