How to use Lasix (furosemide) in patients with impaired renal function, as indicated by a low estimated Glomerular Filtration Rate (eGFR)?

From the Guidelines

Furosemide (Lasix) dosing should be adjusted in patients with impaired renal function, but the medication remains effective and often necessary even with low eGFR. For patients with mild to moderate renal impairment (eGFR 30-60 ml/min), start with a standard dose of 20-40 mg orally and titrate upward as needed, monitoring response carefully 1. For severe renal impairment (eGFR <30 ml/min), higher doses are typically required - start with 40-80 mg orally and increase gradually, sometimes up to 160-200 mg per dose if needed to achieve diuresis. Continuous monitoring of electrolytes (particularly potassium, sodium, and chloride), renal function, and fluid status is essential, as noted in the guidelines for the diagnosis and treatment of acute and chronic heart failure 1. Blood pressure should be checked regularly as these patients are at higher risk for hypotension. The increased dosing requirement occurs because furosemide must reach the tubular lumen via active secretion in the proximal tubule to exert its effect, and this process is impaired in kidney disease. Additionally, accumulated uremic toxins can compete with furosemide for protein binding and transport. If oral furosemide is ineffective despite dose escalation, switching to intravenous administration or adding a thiazide diuretic (for eGFR >30 ml/min) or metolazone (for any eGFR level) may enhance diuretic response through sequential nephron blockade, as suggested by the guidelines for the diagnosis and management of heart failure 1.

Some key points to consider when using Lasix in patients with impaired renal function include:

• The importance of monitoring renal function and adjusting the dose accordingly 1
• The potential for increased dosing requirements in patients with severe renal impairment 1
• The need for careful monitoring of electrolytes and fluid status 1
• The potential benefits of adding a thiazide diuretic or metolazone to enhance diuretic response 1

From the FDA Drug Label

In patients with renal insufficiency, reversible elevations of BUN may occur and are associated with dehydration, which should be avoided, particularly in patients with renal insufficiency Furosemide tablets may increase the ototoxic potential of aminoglycoside antibiotics, especially in the presence of impaired renal function Furosemide tablets can increase the risk of cephalosporin-induced nephrotoxicity even in the setting of minor or transient renal impairment.

The use of Lasix (furosemide) in patients with impaired renal function, as indicated by a low eGFR, requires careful monitoring. Patients with renal insufficiency are at risk of reversible elevations of BUN and dehydration, which should be avoided. Additionally, furosemide may increase the ototoxic potential of certain antibiotics and the risk of nephrotoxicity with certain other medications.

• Monitor serum electrolytes, CO2, creatinine, and BUN frequently during the first few months of Furosemide therapy and periodically thereafter.
• Correct any abnormalities or temporarily withdraw the drug if necessary.
• Avoid using Furosemide with certain medications, such as aminoglycoside antibiotics and cisplatin, in patients with impaired renal function.
• Use Furosemide with caution in patients with renal insufficiency and monitor renal function closely 2 2.

From the Research

Using Lasix (Furosemide) in Patients with Impaired Renal Function

• The use of Lasix (furosemide) in patients with impaired renal function, as indicated by a low estimated Glomerular Filtration Rate (eGFR), requires careful consideration of the potential effects on renal function and electrolyte balance 3, 4.
• Studies have shown that furosemide can decrease the weight gain between dialyses and increase sodium excretion rate in patients with end-stage chronic renal failure, without affecting blood pressure, creatinine clearance, or urinary excretion of potassium and nitrogen 4.
• However, high doses of furosemide may promote calcium wasting, which can facilitate the development of secondary hyperparathyroidism (HPT2) in patients with chronic kidney disease (CKD) 5.
• The relationship between loop diuretic dosing and acute changes in renal function during hospitalization for heart failure has been investigated, and it was found that furosemide exposure is associated with a small increase in creatinine and decrease in eGFR, but explains little of the variability in renal function during hospitalization 3.
• In patients with CKD and high residual proteinuria, a cautious uptitration of loop diuretic dosage in addition to combined half doses of ACEI and ARB may better decrease proteinuria than uptitration to full dose of combined ACEI and ARB, but this effect is partly explained by a decrease in eGFR 6.

Considerations for Dosing and Monitoring

• When using Lasix (furosemide) in patients with impaired renal function, it is essential to monitor renal function and electrolyte balance closely, and to adjust the dose accordingly 3, 4.
• The dose of furosemide should be titrated carefully to achieve the desired therapeutic effect, while minimizing the risk of adverse effects such as hypotension, electrolyte imbalance, and worsening renal function 6, 3.
• Patients with CKD should be monitored for signs of secondary hyperparathyroidism, and the use of furosemide should be reappraised in advanced stages of CKD 5.