LASIX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for LASIX (LASIX).
Furosemide inhibits the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle, reducing sodium, chloride, and water reabsorption and increasing urinary output.
| Metabolism | Furosemide is metabolized primarily by glucuronidation via UGT1A1, with minimal hepatic metabolism; about 50% is excreted unchanged in urine. |
| Excretion | Primarily renal excretion (50-80% as unchanged drug) via glomerular filtration and proximal tubular secretion; minor fecal elimination (<5%). |
| Half-life | Terminal elimination half-life is approximately 1.5-2 hours. In renal impairment (CrCl <20 mL/min), half-life may prolong to up to 2-4 hours; in end-stage renal disease or heart failure, may exceed 4 hours. |
| Protein binding | 91-99% bound, primarily to albumin. |
| Volume of Distribution | 0.1-0.2 L/kg in healthy adults; increases in conditions with reduced plasma protein binding (e.g., nephrotic syndrome) or fluid overload (e.g., heart failure) up to 0.3-0.8 L/kg. |
| Bioavailability | Oral: 60-70% (range 50-80%); decreased by food; intravenous: 100%. |
| Onset of Action | Oral: 30-60 minutes. Intravenous: 5 minutes (within 30 minutes of administration). Intramuscular: 30 minutes. |
| Duration of Action | Oral: 4-6 hours. Intravenous: Approximately 2 hours. Diuresis typically ends within 6-8 hours; in renal impairment, duration may be prolonged. |
| Molecular Weight | 330.745 |
| Action Class | High-ceiling Diuretics (Inhibitors of Na+-K+- 2Cl cotransport) |
| Brand Substitutes | Lasipen 40mg Tablet, FRUSAMIDE 40 MG TABLET, Cgfru 40mg Tablet, Frusenex 40mg Tablet, Oroside 40 Tablet, Frusizex 10mg Injection, Urix 10mg/ml Injection, Lasibrace Injection, FRU 20 MG INJECTION, Lasarc 20mg Injection, Casix 20mg Injection, Lasiwin 20mg Injection, Lasitag 20mg Injection |
20-80 mg IV or PO once or twice daily; maximum 600 mg/day IV or PO.
| Dosage form | INJECTABLE |
| Renal impairment | GFR 10-50 mL/min: dose every 12 hours; GFR <10 mL/min: avoid use or use with extreme caution. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: contraindicated or avoid. |
| Pediatric use | 1-2 mg/kg/dose PO or IV every 6-12 hours; maximum 6 mg/kg/day. |
| Geriatric use | Start at 20 mg/day PO or 20 mg IV, titrate slowly due to increased sensitivity and risk of electrolyte disturbances. |
| 1st trimester | Use only if potential benefit justifies risk to fetus. Crosses placenta; case reports of congenital abnormalities, but no clear causal association. Avoid if possible. |
| 2nd trimester | May be used for maternal indications (e.g., hypertension, edema) but monitor fetal growth and amniotic fluid. Risk of electrolyte imbalance in mother and fetus. |
| 3rd trimester | Use with caution; may cause electrolyte disturbances in neonate. Avoid near term if possible due to risk of neonatal diuresis, electrolyte imbalance, and potential for hyperbilirubinemia. |
Clinical note
Comprehensive clinical and safety monograph for LASIX (LASIX).
| Placental transfer | Furosemide crosses the placenta; fetal plasma concentrations reach approximately 3-10% of maternal levels. May cause electrolyte disturbances in fetus. |
| Breastfeeding | Furosemide is excreted into breast milk in small amounts; however, it may suppress lactation. Infant serum concentrations are low and adverse effects are unlikely. Caution in premature infants or those with electrolyte imbalances. Monitor infant for signs of diuresis or electrolyte disturbances. |
■ FDA Black Box Warning
Furosemide is a potent diuretic. If given in excessive amounts, it can lead to profound diuresis with water and electrolyte depletion. Therefore, careful medical supervision is required, and dose and dose schedule must be adjusted to the individual patient's needs.
| Serious Effects |
AnuriaSevere electrolyte depletionHepatic coma or precomaKnown hypersensitivity to furosemide or sulfonamides
| Precautions | Risk of hypovolemia, dehydration, and electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), Ototoxicity, especially with rapid injection or severe renal impairment, Sulfonamide cross-sensitivity |
| Food/Dietary | High sodium intake can counteract diuretic effects. Avoid excessive licorice consumption as it can worsen hypokalemia. Grapefruit juice may increase systemic exposure of furosemide; avoid concurrent use. |
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| Lactation Rating | L2 (Probably Compatible) |
| Teratogenic Risk | Furosemide crosses the placenta. First trimester: limited data, no clear teratogenic pattern; risk cannot be excluded. Second and third trimesters: may cause maternal hypovolemia, decreased placental perfusion, electrolyte imbalances, and fetal dehydration; oligohydramnios reported. Use only if clearly needed. |
| Fetal Monitoring | Monitor maternal blood pressure, serum electrolytes, renal function, and urine output. Fetal monitoring: ultrasound for amniotic fluid volume (risk of oligohydramnios). In high-risk pregnancies, consider fetal heart rate monitoring. |
| Fertility Effects | No known adverse effects on fertility. Furosemide may theoretically affect reproductive function by altering electrolyte balance or causing volume depletion, but no clinical data suggest significant impact. |
| Clinical Pearls | For rapid diuresis in acute pulmonary edema, administer IV furosemide slowly over 1-2 minutes to avoid ototoxicity. Monitor serum potassium closely, especially in patients on digoxin or with hepatic cirrhosis. Higher doses (>80 mg) may require divided doses to prevent peak-related adverse effects. |
| Patient Advice | Take furosemide exactly as prescribed, usually in the morning to avoid nighttime urination. · Weigh yourself daily and report rapid weight gain or loss of more than 2-3 pounds in a day. · Avoid prolonged sun exposure and use sunscreen as furosemide can increase sun sensitivity. · Do not stop taking this medication abruptly; tapering may be needed to avoid rebound fluid retention. |