Intramuscular Furosemide for CHF: Not Recommended
Intramuscular furosemide should be avoided in chronic heart failure; intravenous administration is strongly preferred when parenteral therapy is required, and oral therapy should replace parenteral routes as soon as clinically feasible. 1
Why IM Route Is Inappropriate
The FDA label explicitly states that parenteral furosemide (IM or IV) should be used "only in patients unable to take oral medication or in emergency situations" and must be replaced with oral therapy as soon as practical. 1
Intramuscular injection offers no clinical advantage over IV administration and introduces unnecessary pain, unpredictable absorption, and delayed onset of diuresis compared to the rapid effect achieved with slow IV push. 1
Guidelines from the European Society of Cardiology and American College of Cardiology consistently recommend IV furosemide 20–40 mg bolus (given over 1–2 minutes) as the standard parenteral route for acute decompensated heart failure, with no mention of IM dosing as an acceptable alternative. 2
Appropriate Parenteral Dosing Algorithm
Step 1: Verify Eligibility
- Systolic blood pressure ≥ 90–100 mmHg 2
- Serum sodium > 125 mmol/L 2
- Absence of anuria 2
- Absence of marked hypovolemia 2
Step 2: Select Initial IV Dose
- Diuretic-naïve patients or those on low oral doses (<40 mg/day): Start with 20–40 mg IV bolus over 1–2 minutes 2, 1
- Patients on chronic oral furosemide 40–160 mg/day: Give at least the oral equivalent IV, or 2–2.5× the home dose for acute decompensation 2
- Acute pulmonary edema: Initial dose is 40 mg IV over 1–2 minutes; if inadequate response within 1 hour, increase to 80 mg IV 1
Step 3: Monitor Response
- Place bladder catheter and record urine output hourly, targeting >0.5 mL/kg/h 2
- Target weight loss of 0.5 kg/day (without peripheral edema) to 1.0 kg/day (with edema) 2
- Check electrolytes (especially potassium and sodium) and renal function within 6–24 hours, then every 3–7 days during titration 2
Step 4: Escalate if Needed
- If urine output remains <0.5 mL/kg/h after 2 hours, double the dose but never exceed 160–200 mg per single bolus 2
- Maximum cumulative dose is 100 mg in the first 6 hours and 240 mg in the first 24 hours 2
- If daily requirements exceed 160 mg, switch to continuous infusion at 5–10 mg/hour (maximum rate 4 mg/min) after an initial bolus 2
Step 5: Add Sequential Nephron Blockade
- If adequate diuresis is not achieved after 24–48 hours of maximal loop diuretic therapy (≈160 mg/day), add a thiazide diuretic or aldosterone antagonist rather than further escalating furosemide alone 2
- Options include hydrochlorothiazide 25 mg PO, spironolactone 25–50 mg PO, or metolazone 2.5–5 mg PO 2
Transition to Oral Therapy
- Convert to oral furosemide as soon as the patient can tolerate oral intake and acute decompensation has stabilized. 1
- Oral bioavailability of furosemide is approximately 50%, so the oral dose should be roughly double the effective IV dose (e.g., if 80 mg IV achieved euvolemia, transition to 160 mg PO daily, divided as 80 mg twice daily). 3
- Monitor daily weights and adjust the oral dose to maintain dry weight; most heart failure patients require indefinite diuretic therapy. 2
Common Pitfalls to Avoid
- Do not use IM furosemide when IV access is available; the IM route delays onset and provides no benefit over IV administration. 1
- Do not administer furosemide to hypotensive patients (SBP <90 mmHg) expecting hemodynamic improvement; it worsens tissue perfusion and can precipitate cardiogenic shock. 2
- Do not exceed 160 mg/day furosemide without adding a second diuretic class; the ceiling effect offers no additional benefit and raises adverse-event risk. 2
- Do not withhold higher-dose furosemide out of fear of mild azotemia; transient renal function worsening is acceptable when the patient remains asymptomatic and volume status improves. 2