Pharmacokinetics
Absorption
Bioavailability
Mean oral bioavailability of furosemide from commercially available tablets and oral solution is 64% and 60%, respectively.
Commercially available tablets and oral solution are bioequivalent.
Onset
Following oral administration, onset of diuresis occurs within 30 minutes to 1 hour; maximal effect after 1–2 hours.
Following IV administration, diuresis occurs within 5 minutes and peaks within 20–60 minutes.
Onset of diuresis after IM administration occurs somewhat later than after IV administration.
Maximum hypotensive effect may not be apparent until after several days of therapy.
Duration
Diuretic effect persists 6–8 hours following oral administration and approximately 2 hours following IV administration.
Food
Food does not appear to affect diuretic effect.
Special Populations
In patients with severely impaired renal function, the diuretic response may be prolonged.
Distribution
Extent
Crosses the placenta and is distributed into milk.
Plasma Protein Binding
Approximately 95% bound to plasma proteins (mainly albumin) in both normal and azotemic patients.
Elimination
Metabolism
Metabolized in the liver to the defurfurylated derivative, 4-chloro-5-sulfamoylanthranilic acid.
Elimination Route
Rapidly excreted in urine by glomerular filtration and by secretion from the proximal tubule.
Approximately 50% of an oral dose and 80% of an IV or IM dose are excreted in urine within 24 hours; 69–97% of these amounts is excreted in the first 4 hours. The remainder of the drug is eliminated by nonrenal mechanisms including degradation in the liver and excretion of unchanged drug in the feces.
Half-life
Biphasic; terminal half-life is approximately 2 hours.
Special Populations
Hepatic or renal impairment prolongs the elimination half-life of the drug.
In patients with marked renal impairment without liver disease, nonrenal clearance is increased to the extent that up to 98% of the drug is cleared within 24 hours.
Not removed by hemodialysis.
Stability
Storage
Oral
Solution or Tablets
Tight, light resistant containers at 15–30°C.
Parenteral
Injection
15–30°C; protect from light. Discard unused portion.
Compatibility
Parenteral
Do not mix with strongly acidic solutions (i.e., pH < 5.5), such as those containing ascorbic acid, amrinone, cirpfloxacin, labetolol, tetracycline, milrinone, epinephrine, or norepinephrine, because furosemide may be precipitated.
Solution Compatibility
| Compatible |
| Alcohol 5% and dextrose 5% |
| Amino acids 4.25%, dextrose 25% |
| Dextrose 5% in Ringer’s injection, lactated |
| Dextrose 5% in sodium chloride 0.9% |
| Dextrose 5, 10, or 20% in water |
| Invert sugar 10% in Electrolyte #1 |
| Mannitol 20% |
| Ringer’s injection, lactated |
| Sodium chloride 0.9% |
| Sodium lactate (1/6) M |
| Incompatible |
| Fructose 10% in water |
| Invert sugar 10% in Electrolyte #2 |
Drug Compatibility
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