What is the preferred initial diuretic, furosemide (Lasix) or torsemide, in the management of acute heart failure?

Furosemide vs. Torsemide in Acute Heart Failure

Furosemide is the preferred initial diuretic in the management of acute heart failure based on established clinical guidelines and FDA labeling. 1, 2

Initial Diuretic Selection

Furosemide

• Specifically indicated for acute pulmonary edema and congestive heart failure by FDA labeling 2
• Recommended initial dose: 20-40 mg IV bolus 1
• For patients on chronic oral diuretic therapy, initial IV dose should be at least equivalent to their oral dose 1
• Maximum recommended dose: <100 mg in first 6 hours and <240 mg during first 24 hours 1

Torsemide

• FDA labeling indicates use for edema associated with heart failure, but does not specifically mention acute heart failure 3
• Initial oral dosing for heart failure: 10-20 mg once daily 3
• No specific IV dosing recommendations for acute heart failure in guidelines 1, 4

Evidence-Based Considerations

Efficacy

• European Society of Cardiology guidelines specifically recommend furosemide as the initial diuretic for acute heart failure 1
• Annals of Emergency Medicine clinical policy recommends furosemide in combination with nitrate therapy for moderate-to-severe pulmonary edema 1
• Limited head-to-head studies comparing IV torsemide to IV furosemide in acute heart failure

Pharmacological Differences

• Torsemide has more predictable bioavailability (80-100%) compared to furosemide (10-100%) 5
• Torsemide has a longer half-life (approximately 3.5 hours vs. 1.5 hours for furosemide) 5
• Torsemide is more rapidly absorbed than furosemide in heart failure patients 5

Clinical Outcomes

• Observational data suggest similar or potentially better outcomes with torsemide compared to furosemide, but these findings are confounded by baseline differences in patient populations 6, 7
• In the ASCEND-HF trial analysis, torsemide-treated patients had more severe disease at baseline but similar outcomes after adjustment 6

Practical Approach to Diuretic Management in Acute Heart Failure

1. Initial therapy: IV furosemide 20-40 mg bolus (or equivalent to home oral dose if on chronic therapy) 1
2. Monitoring response: Assess urine output, symptoms, and vital signs frequently in the initial phase 1
3. Dose adjustment: If inadequate response, increase dose according to renal function and history of chronic diuretic use 1
4. Consider continuous infusion: For volume overload, continuous infusion may be considered after the initial bolus 8
5. Combination therapy: For diuretic resistance, consider adding thiazides or aldosterone antagonists 1

Potential Adverse Effects to Monitor

• Hypokalaemia, hyponatraemia, hyperuricaemia
• Hypovolaemia and dehydration
• Neurohormonal activation
• Hypotension following ACE inhibitor/ARB therapy
• Worsening renal function 1

Special Considerations

• Patients with hypotension (SBP <90 mmHg), severe hyponatremia, or acidosis may have poor response to diuretic therapy 1
• Consider alternative treatments such as IV vasodilators to reduce the need for high-dose diuretic therapy 1
• Diuretics should be administered judiciously given the potential association between diuretics, worsening renal function, and long-term mortality 1

While torsemide has theoretical advantages over furosemide in terms of bioavailability and pharmacokinetics, current guidelines and clinical evidence support furosemide as the preferred initial diuretic in acute heart failure management. Future randomized comparative effectiveness trials are needed to definitively establish the optimal diuretic choice.