Furosemide

Brand

Lasix

Availability

  • Tablets: 20 mg, 40 mg, 80 mg
  • Solutions: 8 mg/mL, 10 mg/mL
  • Injection: 10 mg/mL IM or IV

Pharmacology

Furosemide is a powerful loop diuretic which inhibits the reabsorption of sodium and chloride, as well as potassium to some degree. In addition to diuretic activity it appears to have a direct effect on the blood flow through vasculature beds. It has also been shown to relieve pulmonary congestion, and to reduce filling pressures in the left ventricle in congestive heart failure.

It is rapidly absorbed and results may be seen in 20 minutes to an hour. The maximum effect of this drug occurs anywhere from 2-4 hours after ingestion, and its action lasts for up to 8 hours. Furosemide exhibits an antihypertensive effect.

It is metabolized in the liver and excreted in the urine. It is an effective drug for use in those with a reduced glomerular filtration rate.

Indications

For use in CHF (congestive heart failure), acute pulmonary edema, nephrotic syndrome, hepatic cirrhosis, and ascites.
Adjunctive therapy in hyperkalemia (high blood levels of potassium) in small animals. May be helpful in rats with severe cases of pneumonia.

Drug Interactions or Contraindications

  • Can cause fetal abnormalities and is therefore contraindicated in pregnancy.
  • It is contraindicated in states of anuria, hepatic coma, and when electrolyte depletion is evidenced.
  • Potentiates hypotensive effects of other antihypertensive agents.
  • Can cause salicylate toxicity when used together.
  • Furosemide with aminoglycosides potentiate ototoxicity use together cautiously.
  • NSAIDs (e.g., ibuprofen, meloxicam) inhibit the diuretic response use together with caution.

Adverse Reactions

CV: volume depletion and dehydration

EENT: ototoxicity (transient hearing loss)

GI: diarrhea

Metabolic: fluid and electrolyte imbalances

Dosage Recommendations

1 mg/kg to 4 mg/kg, SQ or IM, q4hr to q6hr; or 5 mg/kg to 10 mg/kg, SQ, IM, q12hr (as diuretic for edema, pulmonary congestion, ascites)  1, 34, 41, 42

or

0.3 mg/kg to 4 mg/kg, PO, SQ, IM, IV, q12hr to q24hr (congestive heart failure) 34

or

5 mg/kg to 10 mg/kg, SQ or IM, q12hr  1, 26, 27

or

2 mg/kg to 10 mg/kg, PO, SQ, IM, q12hr  35

Considerations

  • When used concomitantly with corticosteroids, the chance of hypokalemia will be enhanced. Stop drug in cases of severe diarrhea.
  • Tablets should be stored at cool room temperature in dark containers away from light.

Cross-references

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