Pharm
Furosemide
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Furosemide
, Lasix
See Also
Loop Diuretic
Indications
See
Loop Diuretic
Precautions
Lasix (named for LAst SIX) is only effective for 6 hours
Optimal dosing is given at least twice daily (patient otherwise is
Sodium
avid 18 hours/day)
Pharmacokinetics
Oral
Onset: 1 hour
Half-Life
: 1 to 1.5 hours
Duration: 6 to 8 hours
Highly variable
Bioavailability
on oral ingestion (typically 50%, varies between 10 and 90%)
Increased
Bioavailability
when taken with meals
Gastrointestinal absorption is markedly decreased in severe edema (e.g. CHF exacerbation)
Contrast with
Torsemide
which has excellent and consistent
Bioavailability
Intravenous
Onset: 5 minutes
Duration: 2 hours
Protein
-Binding: 95%
Eliminated unchanged in urine
Higher doses (2-3x) required for
Nephrotic Syndrome
Renal dysfunction results in decreased response and increased
Half-Life
Only 15-20% of Furosemide dose is delivered to the renal tubule in stage 5 CKD
Mechanism
See
Loop Diuretic
Dosing
Oral (adults)
Start: 20 to 40 mg orally daily to twice daily
Twice daily dosing is recommended due to short duration of activity
Maximum: 600 mg/day (rare to exceed 400 mg/day)
Peak effect at 1 to 1.5 hours after oral dose
Duration: 6-8 hours
Dosing
Intravenous (adults)
Intravenous dose is typically one half of oral dose
In exacerbations, the oral dose is often used IV
Administer slowly over 1-2 minutes
Doses higher than 80 mg should infuse slowly to avoid
Ototoxicity
Bolus
Dose 20 to 40 mg IV (0.5-1.0 mg/kg, max 2 mg/kg)
In CHF exacerbations, 60 mg IV is often given
In
Renal Insufficiency
, consider starting dose = 40 * sCr
Where sCr =
Serum Creatinine
Reflects the diminishing effect of Furosemide as
Serum Creatinine
increases (and GFR drops)
Pharmacokinetics
Onset: Diuresis starts within 10 minutes
Peak effect in 10-30 minutes
Duration: 6 hours
Peak
Diuretic
effect of repeat dosing is 25% of the first dose
Compensatory
Sodium
retention may be overcome by frequent IV doses or continuous infusion
Maximum effective dose (ceiling dose)
Chronic Kidney Disease
or
Nephrotic Syndrome
: 80 to 200 mg
Congestive Heart Failure
or
Cirrhosis
: 40-80 mg
Dosing
Intravenous Infusion (adults)
Background
More effective at maintaining a constant increased
Urine Output
with less adverse effects (e.g.
Ototoxicity
)
Maximum diuresis at 3 hours after continuous infusion started
Precautions
Very high dose Furosemide infusions (4 mg/min) risk
Ototoxicity
Loading dose: 40-200 mg
Loading doses higher than 80 mg should infuse slowly to avoid
Ototoxicity
Infusion dose
Start: 10-20 mg/hour (0.25 to 0.75 mg/kg/hour) IV
Maximum: 40 mg/hour IV
Dosing
Child
IV/IM/PO
Start: 0.5 to 2 mg/kg/dose IV/IM/PO every 6 to 12 hours
Max: 6 mg/kg/dose
Intravenous Infusion
Start: 0.05 mg/kg/hour and titrate
Adverse Effects
See
Loop Diuretic
Ototoxocity
See
Loop Diuretic
Most common with high doses or rapid infusion rates (>4 mg/min)
Decreased
Thyroid Hormone
levels
Associated with Furosemide doses >80 mg/day
Drug Interactions
Warfarin
Furosemide displaces
Warfarin
from
Protein
binding and increases
Warfarin
levels and INR
Cyclosporine
Cyclosporine
decreases
Uric Acid
excretion, and increased gout risk when used with Furosemide
Lithium
Avoid use with Furosemide
Agents that decrease Furosemide
Diuretic
effect
Indomethacin
Probenacid
Safety
Pregnancy Category C
Unknown Safety in
Lactation
Resources
Furosemide Tablets (DailyMed)
https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=e3a5db0e-bf6c-4ea9-9133-c3f215c856d0
Furosemide Intravenous Solution (DailyMed)
https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=39fd32f2-6bb7-4a65-d298-e48d26bc80c7
References
(2021) Presc Lett, Resource #370507, Commonly Used
Diuretic
s
(2020) Med Lett Drugs Ther 62(1598): 73-80
Hamilton (2020) Tarascon Pocket Pharmacopoeia
Olson (2020) Clinical
Pharmacology
, Medmaster Miami, p. 62-3
Won Oh (2015) Electrolyte Blood Press 13(1):17-21 +PMID: 26240596 [PubMed]
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