How does Lasix (furosemide) affect renal function?

From the Guidelines

Lasix (furosemide) can have a detrimental effect on renal function, particularly with prolonged use or at higher doses, leading to a dose-dependent decline in eGFR and increased risk of hospital admission and mortality. The mechanism of action of furosemide involves inhibiting the sodium-potassium-chloride cotransporter in the thick ascending limb of the loop of Henle, which can disrupt the kidney's ability to concentrate urine and lead to increased excretion of electrolytes and water in the urine 1.

Key Points to Consider

• Furosemide typically begins working within 30-60 minutes after oral administration and within minutes when given intravenously, with a maximal effect achieved after the first dose and a reduced effect with subsequent doses 1.
• The use of loop diuretics, such as furosemide, is associated with more severe renal decline, higher risk of hospital admission, and increased mortality rate in patients with heart failure 1.
• Regular monitoring of electrolytes, kidney function, and blood pressure is essential during Lasix therapy, especially when initiating treatment or adjusting doses 1.
• The dose of furosemide may need to be increased over time due to reduced kidney perfusion and function, and patients may become unresponsive to high doses of diuretic drugs if they consume large amounts of dietary sodium or have significant impairment of renal function or perfusion 1.

Clinical Implications

• Close monitoring of renal function and electrolytes is crucial when using Lasix, particularly in patients with pre-existing renal impairment or those at risk of developing renal decline.
• The use of furosemide should be tailored to the individual patient's needs, with careful consideration of the potential risks and benefits, and regular adjustments to the dose and monitoring schedule as needed 1.

From the FDA Drug Label

In patients at high risk for radiocontrast nephropathy, furosemide can lead to a higher incidence of deterioration in renal function after receiving radiocontrast compared to high-risk patients who received only intravenous hydration prior to receiving radiocontrast. Furosemide tablets combined with angiotensin converting enzyme inhibitors or angiotensin II receptor blockers may lead to severe hypotension and deterioration in renal function, including renal failure. One study in six subjects demonstrated that the combination of furosemide and acetylsalicylic acid temporarily reduced creatinine clearance in patients with chronic renal insufficiency.

Key Points:

• Furosemide may worsen renal function in patients at high risk for radiocontrast nephropathy.
• Combination of furosemide with certain medications (e.g., angiotensin converting enzyme inhibitors, angiotensin II receptor blockers, NSAIDs) may lead to deterioration in renal function.
• Monitoring of renal function is recommended, especially in patients with pre-existing renal insufficiency. 2, 3, 3

From the Research

Effects of Lasix on Renal Function

• Lasix (furosemide) is a potent loop diuretic that inhibits the Na(+)-K(+)-2Cl(-) cotransporter (NKCC)-2 in the ascending limb of the loop of Henle, which can lead to undesirable consequences such as worsening of kidney function and unpredictable effects on sodium balance 4.
• The use of furosemide can compromise renal blood flow and glomerular filtration rate, particularly if renal function is already compromised, due to activation of tubuloglomerular feedback or renin release 4.
• Furosemide infusion therapy has been associated with moderately negative cumulative fluid balances, electrolyte shifts, and mild transient worsening of renal function 5.
• In patients with acute kidney injury, furosemide may be useful in achieving fluid balance, but its clinical roles remain uncertain and the current evidence does not suggest that it can reduce mortality 6.
• The use of small doses of furosemide in chronic kidney disease patients with residual renal function undergoing hemodialysis has been shown to increase urinary volume and sodium excretion compared to patients who do not use this drug 7.

Renal Effects of Furosemide

• Furosemide can cause a decrease in glomerular filtration rate (GFR) and renal blood flow, particularly in patients with pre-existing renal disease 4, 5.
• The drug can also lead to electrolyte imbalances, including hypokalemia, hypomagnesemia, and hypocalcemia 5.
• In patients with nephrotic syndrome, furosemide may be used to treat edema, but its efficacy and safety are still debated 8.

Clinical Implications

• The use of furosemide requires careful monitoring of renal function, electrolyte levels, and fluid balance to minimize its adverse effects 4, 6, 5.
• Patients with pre-existing renal disease or those undergoing hemodialysis may require adjusted doses of furosemide to avoid worsening of renal function 7.
• Further studies are needed to fully understand the effects of furosemide on renal function and to determine its optimal use in different clinical settings 4, 8.