Furosemide

Loop diuretic, Diuretic

Furosemide

Lasix

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Titration strategies

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Effects

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Summary

Classes

Loop diuretic, Diuretic

Pharmacy

Starting dose

20-40 mg PO/IV; titrate by clinical response. In diuretic-resistant heart failure or CKD, doses to 200 mg or higher may be needed

Preparations

20, 40, 80 mg tablets; 10 mg/mL oral solution; 10 mg/mL IV

US FDA Max

600 mg/d typical practical ceiling in heart failure

Pharmacology

Routes

Oral, IV, IM

Onset

IV: 5 minutes; PO: 30-60 minutes

Duration

IV: ~2 hours; PO: 6-8 hours

Half-life

1.5-2 hours (longer in renal failure)

Bioavailability

~50% (oral; highly variable, 10-100%, hence the standard 1:2 IV-to-PO conversion)

Pregnancy

Avoid where possible; can reduce uteroplacental perfusion and produce neonatal electrolyte disturbance. Reserved for compelling indications.^{[citation needed]}

Legal status

Rx-only in US

Purported mechanism

Furosemide blocks the Na+/K+/2Cl- cotransporter (NKCC2) on the apical membrane of thick ascending limb cells, abolishing the medullary osmotic gradient and producing brisk natriuresis, kaliuresis, and free-water clearance.▲0▼ Loop diuretics are the most potent diuretics in routine clinical use because the ascending limb reabsorbs ~25% of filtered sodium. Ototoxicity (especially with rapid IV bolus), hypokalemic metabolic alkalosis, hyperuricemia, and gout flare are the characteristic side effects.