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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) due to heart failure, liver disease, and kidney disease. It is also used to treat high blood pressure, usually in combination with other antihypertensives.
## Primary Indications
* Edema associated with congestive heart failure (CHF), liver cirrhosis, and renal disease.
* Hypertension.
## Adult Dosing
* **Edema:** Initial dose is typically 20-80 mg orally once daily. Doses may be increased by 20-40 mg every 6-8 hours as needed. The usual maintenance dose is 20-80 mg once or twice daily.
* Intravenous (IV) or intramuscular (IM) doses are typically 20-40 mg once daily. If ineffective, doses can be increased by 20 mg every 2 hours, or given as a continuous infusion.
* Maximum oral dose is generally 600 mg daily, though higher doses have been used under close supervision in severe cases.
* Maximum IV/IM dose is generally 100 mg in a single dose or 200 mg daily for less severe cases, but higher doses may be used cautiously.
* **Hypertension:** Doses typically range from 40 mg orally twice daily. It is often used in combination with other antihypertensives. Furosemide is generally not a first-line agent for hypertension unless edema is also present.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose given orally once or twice daily. Maximum initial dose: 40 mg/day. Doses may be increased by 1-2 mg/kg/dose every 6-8 hours. Usual maintenance dose: 1-4 mg/kg/day divided into 1-2 doses. Maximum maintenance dose: 6 mg/kg/day.
* IV/IM: 1 mg/kg/dose given intravenously or intramuscularly once or twice daily. Maximum dose: 40 mg/day. In premature infants, doses should be adjusted more cautiously.
## Dose Adjustments
* **Renal Impairment:** Dose reduction is often necessary in patients with renal impairment. For IV administration, consider a continuous infusion to maintain a consistent diuresis.
* **Hepatic Impairment:** Use with caution; monitor for electrolyte imbalances and hepatic encephalopathy.
## Contraindications
* Anuria.
* History of hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, headache, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), dehydration, hypotension, fatigue.
* **Serious:** Ototoxicity (especially with rapid IV administration or high doses), severe rash (including Stevens-Johnson syndrome), aplastic anemia, acute kidney injury.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effects; increased risk of renal impairment.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Increased risk of lithium toxicity due to decreased renal clearance.
* **Antihypertensives:** Additive hypotensive effects.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Renal function (BUN, creatinine).
* Blood pressure.
* Urine output.
* Serum glucose and uric acid (especially in patients with diabetes or gout).
* Hearing (for signs of ototoxicity).
## Clinical Pearls
* Administer oral furosemide with food or milk to minimize gastrointestinal upset.
* To minimize ototoxicity, administer IV furosemide slowly (over 30-60 minutes) or via continuous infusion, especially at higher doses.
* Rapid diuresis can lead to dehydration and electrolyte depletion; monitor closely.
* Potassium supplementation or potassium-sparing diuretics may be required to prevent or treat hypokalemia.
* Furosemide can increase blood glucose and uric acid levels.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the official prescribing information and current clinical guidelines for complete details. Dosing and recommendations may vary based on individual patient factors and local protocols.*
