IV Furosemide Dosing Equivalent to Oral Dose
For patients already on chronic oral furosemide therapy, the initial IV dose should be at least equivalent to their oral dose (1:1 conversion), not half the oral dose. 1
Conversion Rationale
The European Society of Cardiology guidelines explicitly state that for established heart failure patients on chronic oral diuretic therapy, the IV furosemide bolus should be "at least equivalent to oral dose." 1 This recommendation accounts for the clinical context where rapid diuresis is needed and acknowledges that IV administration provides more reliable bioavailability in acutely decompensated patients. 1
Key Dosing Principles
For patients on chronic oral furosemide: Give the same dose IV as they were taking orally (e.g., if taking 40 mg PO, give 40 mg IV). 1
For new-onset heart failure or diuretic-naive patients: Start with 40 mg IV. 1
Maximum single IV dose: 160-200 mg, though higher doses may occasionally be used with close monitoring. 1
IV administration technique: Give slowly over 1-2 minutes for bolus dosing. 2
Important Clinical Context
Why 1:1 Conversion in Acute Settings
While oral furosemide has approximately 50% bioavailability compared to IV 3, 4, the guideline recommendation for 1:1 conversion in acute decompensated heart failure reflects several clinical realities:
- Acutely ill patients often have gut edema and unpredictable oral absorption. 3
- The goal is rapid, reliable diuresis requiring immediate IV effect. 1
- The "at least equivalent" language allows for dose escalation if needed. 1
When Converting IV Back to Oral (Stable Patients)
When transitioning from IV to oral therapy after stabilization, use approximately 2:1 oral-to-IV ratio due to the 50% oral bioavailability. 5, 3 For example, 40 mg IV twice daily would convert to 80 mg oral twice daily (total 160 mg/day oral). 5
Dose Escalation Strategy
If inadequate response after initial IV dose: 2
- Wait 2 hours, then increase by 20 mg increments. 1
- May give additional dose or increase the dose until desired diuretic effect achieved. 2
- For continuous infusion: Load with 40 mg IV, then infuse 10-40 mg/hour. 1
Critical Monitoring Parameters
- Urine output (should increase within 1 hour of IV administration). 2, 6
- Serum electrolytes (particularly potassium, sodium, chloride). 1, 6
- Renal function (creatinine, BUN). 1, 6
- Blood pressure and volume status. 1, 6
Common Pitfalls to Avoid
Do not use 2:1 oral-to-IV conversion in acute settings: This applies when converting stable patients from IV back to oral, not when initiating IV therapy in someone on chronic oral therapy. 5
Avoid underdosing: Patients on chronic high-dose oral furosemide (e.g., 80-160 mg daily) need equivalent or higher IV doses for acute decompensation, not reduced doses. 1
Monitor for ototoxicity: Particularly with high doses (>160-200 mg) or rapid infusion rates exceeding 4 mg/min. 1, 2
Ensure proper pH for infusions: Furosemide precipitates at pH <7; do not mix with acidic solutions. 2