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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to reduce fluid overload (edema) associated with heart failure, liver disease, and kidney disease, including nephrotic syndrome. It is also used to treat high blood pressure, usually in combination with other antihypertensives.
## Primary Indications
* Edema due to heart failure, cirrhosis, and renal disease.
* Hypertension (often as adjunctive therapy).
## Adult Dosing
* **Edema:** 20-80 mg orally once daily. Doses may be increased by 20-40 mg every 6-8 hours until desired response is achieved. Usual maintenance dose is 20-120 mg orally daily, but may be as high as 600 mg daily in severe cases, divided into 1-2 doses.
* **Hypertension:** 40 mg orally twice daily. Not usually a first-line agent for hypertension unless fluid overload is present.
* **Intravenous (IV) or Intramuscular (IM) Administration:**
* **Edema:** 20-40 mg IV/IM once daily. If inadequate response, doses can be increased by 20 mg every 2 hours. Doses up to 80-100 mg IV/IM once daily may be used in severe edema. For continuous IV infusion, a starting dose of 10 mg/hour after an initial bolus of 20-40 mg may be considered.
## Pediatric Dosing
* **Edema:**
* **Oral:** 1-2 mg/kg/dose orally once daily. May be increased by 1-2 mg/kg/dose every 6-8 hours as needed. Maximum single dose 6 mg/kg. Daily doses are typically 1-4 mg/kg/day divided into 1-2 doses.
* **IV/IM:** 1 mg/kg/dose IV/IM once daily. May be increased by 0.5-1 mg/kg/dose every 2 hours as needed. Maximum single dose 6 mg/kg. For continuous infusion, 0.2-0.5 mg/kg/hour.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in renal impairment due to reduced excretion. However, caution is warranted as high doses can be nephrotoxic.
* **Hepatic Impairment:** Reduced doses may be necessary due to altered metabolism and increased sensitivity to effects.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, headache, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), dehydration, hypotension, polyuria.
* **Less Common/Serious:** Ototoxicity (especially with rapid IV administration or high doses), hyperglycemia, hyperuricemia (gout), rash, Stevens-Johnson syndrome, aplastic anemia, pancreatitis, acute kidney injury.
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **ACE inhibitors and ARBs:** Increased risk of hypotension and renal dysfunction.
* **NSAIDs:** May reduce diuretic and antihypertensive effects, and increase risk of renal dysfunction.
* **Lithium:** Reduced renal clearance, increasing risk of lithium toxicity.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Corticosteroids:** Additive hypokalemia.
## Monitoring
* **Electrolytes:** Serum electrolytes (sodium, potassium, chloride, magnesium, calcium) are crucial, especially with chronic use.
* **Renal function:** Serum creatinine and BUN.
* **Blood pressure:** Monitor for hypotension.
* **Fluid balance:** Daily weights, intake and output.
* **Hearing:** Assess for tinnitus or hearing loss, particularly with high doses or rapid IV administration.
## Clinical Pearls
* Furosemide is a potent diuretic; diuresis can occur rapidly after IV administration.
* Administer IV furosemide slowly (e.g., over 30-60 minutes) to minimize the risk of ototoxicity. Avoid rapid IV push.
* Oral doses are typically given in the morning to reduce nocturia.
* Electrolyte replacement (especially potassium) may be necessary.
* Monitor patients closely for signs of dehydration and electrolyte depletion.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols for definitive guidance. Dosage and indications may vary.*
