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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) and high blood pressure.
## Primary Indications
* Edema associated with congestive heart failure, liver cirrhosis, and renal disease.
* Hypertension (adjunctive therapy).
* Ascites.
## Adult Dosing
* **Edema:**
* Oral: 20 mg to 80 mg once daily. May increase by 20 mg to 40 mg every 6 to 8 hours as needed. Usual maintenance dose: 40 mg to 80 mg once or twice daily. Doses up to 600 mg daily have been used in severe cases, but higher doses increase the risk of adverse effects.
* Intravenous (IV) or Intramuscular (IM): 20 mg to 40 mg once daily. May increase by 20 mg every 2 hours as needed.
* **Hypertension:**
* Oral: 40 mg twice daily. Typically used in combination with other antihypertensives.
* **Ascites:**
* Oral: 40 mg to 80 mg once daily. May increase by 20 mg to 40 mg. Doses up to 200 mg daily are sometimes required.
## Pediatric Dosing
* **Edema:**
* Oral: 1 mg/kg to 2 mg/kg once daily, not to exceed 40 mg per dose. If inadequate response, may increase dose or divide into 2-4 doses. Maximum daily dose is 6 mg/kg.
* IV or IM: 1 mg/kg per dose once daily, not to exceed 20 mg per dose. If inadequate response, may increase dose. Maximum daily dose is 6 mg/kg.
## Dose Adjustments
* **Renal Impairment:** May require higher doses due to reduced renal clearance. Monitor electrolytes and fluid status closely.
* **Hepatic Impairment:** May require dose adjustment; particularly cautious with ascites due to increased risk of hepatic encephalopathy.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
* Severe electrolyte depletion (e.g., hypokalemia, hyponatremia).
## Adverse Effects
* Electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia).
* Dehydration.
* Ototoxicity (hearing impairment, tinnitus), especially with rapid IV administration or high doses.
* Hypotension.
* Hyperglycemia.
* Hyperuricemia (can precipitate gout).
* Dizziness, lightheadedness.
* Rash, photosensitivity.
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **ACE inhibitors and ARBs:** Increased risk of hypotension and renal dysfunction.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Increased risk of lithium toxicity due to decreased renal clearance.
* **NSAIDs:** May reduce the natriuretic and diuretic effect of furosemide.
* **Potassium-sparing diuretics:** May mitigate furosemide-induced hypokalemia, but monitor potassium closely.
## Monitoring
* Serum electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Renal function (BUN, creatinine).
* Fluid status (weight, intake/output, edema).
* Blood pressure.
* Hearing (especially with high doses or rapid IV infusion).
* Blood glucose.
* Uric acid.
## Clinical Pearls
* Oral administration is preferred for chronic conditions; IV or IM for acute fluid overload or when oral absorption is impaired.
* Rapid IV administration (>4 mg/min) can lead to ototoxicity. Infuse IV furosemide slowly, typically over 30-60 minutes.
* Monitor for signs and symptoms of electrolyte depletion, especially hypokalemia, which can lead to arrhythmias. Consider potassium supplementation if necessary.
* Daily weights are crucial for monitoring fluid status in patients with edema.
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*Always consult the most current prescribing information and institutional protocols for complete details and to ensure accuracy.*
