Can Furosemide (Lasix) 40mg decrease Glomerular Filtration Rate (GFR) in patients with Impaired Renal Function?

From the Guidelines

Furosemide 40mg can decrease Glomerular Filtration Rate (GFR) in patients with impaired renal function, particularly in certain clinical situations, such as heart failure, cirrhosis, or nephrotic syndrome. This loop diuretic works by inhibiting sodium and chloride reabsorption in the ascending loop of Henle, which increases urine output and reduces fluid overload. However, in patients with already compromised kidney function, Furosemide can cause acute reductions in GFR through several mechanisms, including volume depletion and subsequent decreased renal perfusion if excessive diuresis occurs, as well as activation of the renin-angiotensin-aldosterone system, causing vasoconstriction of the afferent arteriole and further reducing GFR 1.

Some key points to consider when administering Furosemide to patients with impaired renal function include:

• Starting with lower doses (perhaps 20mg initially) and titrating based on response and renal function may help minimize the risk of worsening GFR
• Careful monitoring of kidney function, electrolytes, and volume status is essential
• Combination with potassium-sparing diuretics or temporary discontinuation may be necessary if significant worsening of renal function occurs
• The renal decline associated with loop diuretics is dose-dependent, with higher doses causing more rapid decline in eGFR, particularly in patients with worsening renal function (WRF) 1
• Monitoring for diuretic adverse events, such as electrolyte imbalance, worsening hypokalaemia, hyperkalaemia, serum creatinine, hepatic encephalopathy, and muscle cramps, is crucial, and temporarily discontinuing diuretics may be necessary in such cases 1.

Overall, the use of Furosemide in patients with impaired renal function requires careful consideration of the potential risks and benefits, as well as close monitoring to minimize the risk of adverse effects on kidney function.

From the FDA Drug Label

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. In patients at high risk for radiocontrast nephropathy Furosemide tablets 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. One study in six subjects demonstrated that the combination of furosemide and acetylsalicylic acid temporarily reduced creatinine clearance in patients with chronic renal insufficiency.

Furosemide 40mg may decrease Glomerular Filtration Rate (GFR) in patients with impaired renal function, especially when combined with other medications such as angiotensin converting enzyme inhibitors or angiotensin II receptor blockers. Additionally, the use of furosemide in patients with chronic renal insufficiency may lead to a temporary reduction in creatinine clearance. It is essential to monitor renal function closely in these patients. 2, 2, 2

From the Research

Furosemide 40mg and Glomerular Filtration Rate (GFR)

• Furosemide is a loop diuretic that can affect renal function, particularly in patients with impaired renal function 3, 4, 5, 6, 7.
• The effect of furosemide 40mg on GFR in patients with impaired renal function is complex and depends on various factors, including the severity of renal impairment and the presence of other comorbidities.

Pharmacokinetics and Pharmacodynamics of Furosemide

• Furosemide is actively secreted by the proximal tubules into the urine, and its diuretic effect is determined by its urinary concentrations 6.
• The severity of acute kidney injury has a significant effect on the diuretic response to furosemide, with a good urinary response considered a proxy for residual renal function 4, 6.
• Furosemide can increase urinary volume and sodium excretion in patients with residual diuresis, but its effects on GFR are not well established 5.

Clinical Studies on Furosemide and GFR

• A study published in 1984 found that furosemide 40mg did not affect the excretion of creatinine and urea-N in the urine, suggesting that it may not have a significant impact on GFR in patients with chronic renal insufficiency 3.
• A study published in 2011 found that chronic use of small doses of furosemide (40mg) in patients with residual diuresis increased urinary volume and sodium excretion, but did not provide information on GFR 5.
• A study published in 2017 found that a single intravenous bolus of furosemide 40mg increased urine output and urinary sodium, potassium, and chloride losses in critically ill patients, but did not provide information on GFR 7.

Conclusion is not allowed, and the response will continue with more information

• The available evidence suggests that furosemide 40mg may not have a significant impact on GFR in patients with impaired renal function, but its effects on urinary volume and sodium excretion can be beneficial in certain clinical contexts 3, 4, 5, 6, 7.
• However, the relationship between furosemide and GFR is complex and requires further study to fully understand its effects on renal function in different patient populations.
• More research is needed to determine the effects of furosemide on GFR in patients with impaired renal function, particularly in the context of acute kidney injury and chronic kidney disease 4, 6.