From the FDA Drug Label
The terminal half-life of furosemide is approximately 2 hours The half-life of furosemide is approximately 2 hours.
- This value is for patients with normal renal function.
- The half-life may be affected by renal function, but the exact half-life in patients with impaired renal function is not directly stated in the label. 1
From the Research
The half-life of furosemide is approximately 0.79 hours in patients with normal renal function, but it can be prolonged up to 24.58 hours in patients with impaired renal function, as shown in a study published in 1977 2. This prolongation occurs because furosemide is primarily eliminated by the kidneys, with a significant portion excreted unchanged in the urine. In renal impairment, the reduced glomerular filtration rate and tubular secretion lead to decreased drug clearance and accumulation in the body. The degree of half-life extension correlates with the severity of renal dysfunction, with more severe renal impairment resulting in longer half-lives. Some studies have reported varying half-lives, such as a study from 1984 that found the half-life to be prolonged in patients with chronic renal insufficiency 3, and another study from 1986 that found the half-life to be extended in patients with severe renal impairment 4. However, the most relevant and recent study on this topic is not available, but based on the available evidence, it is clear that the half-life of furosemide is significantly prolonged in patients with impaired renal function. This pharmacokinetic change has important clinical implications, as patients with kidney disease may require adjusted dosing intervals to prevent drug accumulation while still achieving therapeutic effects. Despite the prolonged half-life, higher doses of furosemide are often needed in renal impairment because the drug must reach sufficient concentrations at its site of action in the renal tubules to overcome the competitive binding of uremic toxins and achieve diuresis. Key points to consider when prescribing furosemide to patients with renal impairment include:
- The severity of renal dysfunction and its impact on drug clearance
- The potential need for adjusted dosing intervals to prevent drug accumulation
- The importance of monitoring renal function and adjusting the dose accordingly
- The potential benefits of using higher doses of furosemide in patients with severe renal impairment, as shown in a study from 1970 5.