What is the preferred initial loop diuretic, Furosemide (Lasix) or Torsemide, for treating edema?

Torsemide vs Furosemide for Treating Edema

Torsemide is preferred over furosemide as the initial loop diuretic for treating edema due to its superior pharmacokinetic profile, greater bioavailability, longer duration of action, and reduced risk of hospitalizations. 1, 2

Pharmacological Differences

• Torsemide has greater bioavailability (80-100%) compared to furosemide (10-100%), resulting in more predictable effects and less variability between oral and IV administration 3
• Torsemide has a longer duration of action (12-16 hours) compared to furosemide (6-8 hours), allowing for once-daily dosing without the paradoxical antidiuresis seen with furosemide 4, 3
• Torsemide appears to promote less excretion of potassium and calcium compared to furosemide, potentially reducing electrolyte abnormalities 3
• Torsemide has been associated with less ototoxicity than furosemide 1

Clinical Outcomes

• A recent meta-analysis of 10 randomized controlled trials with 4,127 patients showed that patients treated with torsemide had significantly reduced risk of:
  • Cardiovascular hospitalizations (RR 1.36 for furosemide vs torsemide, 95% CI 1.13 to 1.65, p = 0.001)
  • Heart failure-related hospitalizations (RR 1.65,95% CI 1.21 to 2.24, p = 0.001)
  • All-cause hospitalizations (RR 1.06,95% CI 1.01 to 1.11, p = 0.02) 2
• No significant difference was found in all-cause mortality between furosemide and torsemide groups (RR 1.02,95% CI 0.91 to 1.15, p = 0.70) 2

Dosing Recommendations

• For edema associated with heart failure:
  • Torsemide: Initial dose of 10-20 mg once daily; can be titrated upward by approximately doubling until desired diuretic response is obtained (maximum 200 mg) 5
  • Furosemide: Initial dose of 20-40 mg once or twice daily; maximum total daily dose of 600 mg 4

Clinical Considerations

• Loop diuretics are the preferred diuretic agents for use in most patients with heart failure due to their ability to:
  • Increase sodium excretion up to 20-25% of filtered load
  • Enhance free water clearance
  • Maintain efficacy unless renal function is severely impaired 4
• Diuretics produce symptomatic benefits more rapidly than any other drug for heart failure, relieving pulmonary and peripheral edema within hours or days 4
• Patients should be monitored for potential adverse effects:
  • Hypokalaemia, hyponatraemia, hyperuricaemia
  • Hypovolaemia and dehydration
  • Neurohormonal activation
  • Hypotension following initiation of ACEI/ARB therapy 4

Special Situations

• In patients with renal impairment:
  • Torsemide may show a better dose-dependent diuretic effect in acute renal failure patients after continuous renal replacement therapy 6
  • Serum creatinine and blood urea nitrogen elimination may be less pronounced with furosemide 6
• For patients with diuretic resistance:
  • Consider combination therapy with thiazides or aldosterone antagonists 4
  • Continuous infusion may be considered after initial bolus dose in patients with volume overload 4

Practical Approach

1. For initial treatment of edema in heart failure patients, start with torsemide 10-20 mg once daily 5, 1
2. Monitor urine output, weight loss, and symptoms of congestion 4
3. If response is inadequate, titrate dose upward by doubling until desired effect is achieved 5
4. Monitor serum electrolytes, renal function, and volume status regularly 4
5. Consider combination therapy with thiazides or aldosterone antagonists for diuretic resistance 4

Remember that diuretics should not be used alone in the treatment of heart failure but should be combined with other guideline-directed medical therapy such as ACE inhibitors/ARBs and beta-blockers 4.