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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium and chloride in the thick ascending limb of the loop of Henle, leading to increased excretion of water, sodium, chloride, potassium, calcium, magnesium, and hydrogen.
## Primary Indications
* Edema associated with congestive heart failure (CHF)
* Edema associated with hepatic cirrhosis
* Edema associated with renal disease, including nephrotic syndrome
* Hypertension (used as adjunctive therapy)
## Adult Dosing
* **Edema:**
* Oral: Initial dose is typically 20-80 mg once daily. May be given as a single dose or divided. Maximum daily dose is 600 mg.
* Intravenous (IV) or Intramuscular (IM): Initial dose is typically 20-40 mg once daily. May be given as a single dose or divided. Maximum daily dose is 600 mg. For acute pulmonary edema, doses of 20-40 mg IV may be given.
* **Hypertension:**
* Oral: Initial dose is typically 40 mg twice daily. May be adjusted based on response.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose once or twice daily. Maximum dose: 6 mg/kg/day.
* IV or IM: 1 mg/kg/dose once or twice daily. Maximum dose: 6 mg/kg/day. For acute pulmonary edema, doses of 1 mg/kg IV may be given. Doses higher than 1 mg/kg/dose IV should be administered by continuous infusion.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with renal insufficiency due to impaired drug excretion. However, caution is advised as higher doses may be needed to achieve a diuretic effect.
* **Hepatic Impairment:** Dose reduction may be necessary.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides
## Adverse Effects
* Electrolyte imbalances: Hypokalemia, hyponatremia, hypochloremia, hypocalcemia, hypomagnesemia
* Dehydration
* Hypotension
* Ototoxicity (especially with rapid IV administration or high doses)
* Hyperuricemia (may precipitate gout)
* Hyperglycemia
* Increased BUN
* Dizziness, lightheadedness
* Rash, photosensitivity
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May decrease the diuretic and antihypertensive effects of furosemide.
* **Lithium:** Furosemide can decrease renal clearance of lithium, increasing lithium levels and risk of toxicity.
* **Antihypertensives:** Additive hypotensive effect.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (especially potassium, sodium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Blood pressure
* Fluid balance (intake and output)
* Weight
* Hearing (especially with high doses or concomitant ototoxic agents)
## Clinical Pearls
* Administer oral furosemide with food or milk to minimize gastrointestinal upset.
* IV furosemide should be administered slowly (e.g., over 1-2 minutes) to reduce the risk of ototoxicity and hypotension. Rapid IV infusion can cause transient hearing loss.
* Monitor closely for signs of dehydration and electrolyte imbalance.
* Furosemide is a potent diuretic; dose titration is often required to achieve desired effect while minimizing adverse effects.
* For patients with severe edema and good renal function, higher doses or continuous IV infusion may be necessary.
* Consider potassium supplementation or potassium-sparing diuretics if hypokalemia is significant or persistent.
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*This information is intended for educational purposes only and does not constitute medical advice. Always consult the most current prescribing information and a healthcare professional for personalized guidance.*
