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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver cirrhosis, and renal disease, as well as hypertension.
## Primary Indications
* Edema (associated with congestive heart failure, liver cirrhosis, renal disease)
* Hypertension (adjunctive therapy)
## Adult Dosing
* **Edema:**
* **Initial:** 20 mg to 80 mg orally once daily.
* **Maintenance:** 20 mg to 120 mg orally every day, or 40 mg to 80 mg orally twice daily. Doses up to 600 mg daily have been used in severe cases, but typically require close monitoring.
* **Hypertension:**
* **Initial:** 40 mg orally twice daily.
* **Maintenance:** Adjust based on response. Typically used as an adjunct when blood pressure is not controlled with other agents.
## Pediatric Dosing
* **Edema:**
* **Initial:** 1 mg/kg to 2 mg/kg orally once daily.
* **Maximum Initial:** 40 mg per dose.
* **Maintenance:** 1 mg/kg to 4 mg/kg orally per day, divided into 1 to 4 doses. Maximum daily dose of 6 mg/kg.
* **Neonates:** Dosing can be more variable; often initiated at 1 mg/kg every 12-24 hours.
## Dose Adjustments
* **Renal Impairment:** Higher doses may be required due to impaired excretion. Dose should be carefully titrated.
* **Hepatic Impairment:** Dose reduction may be necessary due to altered pharmacokinetics.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides.
* Severe electrolyte depletion (e.g., hyponatremia, hypokalemia).
## Adverse Effects
* **Common:** Dizziness, lightheadedness, electrolyte imbalance (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), dehydration, hypotension, hyperglycemia.
* **Serious:** Ototoxicity (especially with rapid IV administration or high doses), severe rash, Stevens-Johnson syndrome, aplastic anemia, acute kidney injury.
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce the diuretic and antihypertensive effect of furosemide.
* **ACE Inhibitors/ARBs:** Increased risk of severe hypotension and acute kidney injury, especially in volume-depleted patients.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** May reduce renal clearance of lithium, increasing the risk of lithium toxicity.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Blood pressure
* Fluid balance (intake and output, weight)
* Blood glucose (especially in diabetic patients)
* Auditory function (especially with high doses or prolonged use)
## Clinical Pearls
* Furosemide's onset of action is rapid: approximately 1 hour orally, and within minutes intravenously.
* Administer IV furosemide slowly to minimize ototoxicity risk.
* Oral administration is generally preferred for chronic management of edema.
* Electrolyte monitoring and replacement are crucial, particularly for potassium. Consider potassium-sparing diuretics or potassium supplementation if hypokalemia is a concern.
* Monitor for signs of dehydration and hypotension.
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*Please verify current prescribing information and consult with the prescribing clinician for specific patient management.*
