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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium and chloride in the ascending limb of the loop of Henle, leading to increased excretion of water, sodium, chloride, potassium, calcium, and magnesium.
## Primary Indications
* Edema associated with congestive heart failure (CHF)
* Edema associated with liver disease (ascites)
* Edema associated with renal disease, including nephrotic syndrome
* Hypertension (may be used as adjunctive therapy, particularly in patients with concomitant edema or renal impairment)
## Adult Dosing
* **Edema:**
* Oral: 20 mg to 80 mg once daily. Doses may be increased by 20 mg to 40 mg every 6 to 8 hours as needed.
* Alternatively, a dose of 20 mg to 40 mg every day or every other day can be used.
* Maximum oral dose: 600 mg daily in patients with severe edema, though doses higher than 80 mg to 100 mg may not be more effective and increase the risk of adverse effects.
* Intravenous (IV): 20 mg to 40 mg once daily. If insufficient response, doses may be increased by 20 mg every 2 hours.
* Maximum IV dose: 100 mg as a single dose, or up to 200 mg in refractory cases, though higher doses are generally avoided. Continuous infusion may be considered for refractory edema.
* **Hypertension:**
* Oral: 40 mg twice daily.
* Furosemide is generally not a first-line agent for hypertension unless there is concurrent edema or renal impairment.
## Pediatric Dosing
* **Edema:**
* Oral: 1 mg/kg to 2 mg/kg once daily. Doses may be increased by 1 mg/kg every 6 to 8 hours as needed.
* Maximum oral dose: 6 mg/kg per day.
* Intravenous (IV): 1 mg/kg once daily. If insufficient response, doses may be increased by 1 mg/kg every 2 hours.
* Maximum IV dose: 2 mg/kg per dose.
## Dose Adjustments
* **Renal Impairment:** Higher doses may be required in patients with severe renal impairment due to impaired drug absorption and decreased tubular secretion. Titrate to response.
* **Hepatic Impairment:** May require dose adjustment due to altered pharmacokinetics and increased sensitivity to electrolyte and fluid shifts.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides (caution with cross-reactivity).
## Adverse Effects
* **Common:** Dizziness, lightheadedness, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), dehydration, hypotension, azotemia.
* **Less Common:** Hyperuricemia, hyperglycemia, ototoxicity (especially with rapid IV administration or high doses), rash, photosensitivity, pancreatitis, blood dyscrasias (thrombocytopenia, leukopenia, aplastic anemia), hypercholesterolemia, hypertriglyceridemia.
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce natriuretic and diuretic effects, potentially worsening renal function.
* **ACE Inhibitors/ARBs:** Increased risk of hypotension and acute kidney injury, especially in volume-depleted patients.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, increasing lithium toxicity risk.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Fluid status (weight, intake/output)
* Blood pressure
* Blood glucose (in diabetic patients)
* Uric acid (in patients with gout)
* Hearing (especially with high doses or risk factors for ototoxicity)
## Clinical Pearls
* Furosemide is typically administered orally in the morning to minimize nocturia.
* For patients with severe edema or those who are volume-depleted, careful titration is crucial to avoid excessive diuresis and electrolyte disturbances.
* Rapid IV administration can lead to ototoxicity. Administer IV furosemide slowly (e.g., over 30-60 minutes).
* In patients with heart failure, continuous infusion of furosemide may be more effective than intermittent bolus doses for managing refractory edema.
* Monitor for signs of dehydration and electrolyte depletion, particularly hypokalemia, which can lead to cardiac arrhythmias.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for clinical judgment. Always consult the most current prescribing information and relevant clinical guidelines before making therapeutic decisions.*
