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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) from conditions such as heart failure, liver disease, and kidney disease. It works by inhibiting the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle, leading to increased excretion of sodium, chloride, potassium, calcium, and magnesium.
## Primary Indications
* Edema associated with congestive heart failure (CHF)
* Edema associated with liver cirrhosis
* Edema associated with renal disease, including nephrotic syndrome
* Hypertension (less common as monotherapy, often used adjunctively)
## Adult Dosing
* **Edema:**
* Initial dose: 20-80 mg orally once daily.
* Dose may be increased by 20-40 mg every 6-8 hours as needed based on response.
* For more severe edema, doses may be given twice daily.
* Maximum oral dose: Typically 600 mg daily, but higher doses have been used under close supervision for refractory edema.
* **Hypertension:**
* Initial dose: 40 mg orally twice daily.
* Not usually a first-line agent.
## Pediatric Dosing
* **Edema:**
* Initial dose: 1-2 mg/kg orally once daily.
* Dose may be increased by 1-2 mg/kg every 6-8 hours as needed.
* Maximum oral dose: 6 mg/kg/day.
* Parenteral dosing typically follows similar mg/kg recommendations, but always confirm with specific institutional protocols or guidelines for IV administration.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with renal impairment due to reduced renal clearance. However, patients with severe renal failure may have a diminished response to furosemide.
* **Hepatic Impairment:** Dose may need to be reduced in patients with severe hepatic impairment, as they may be more sensitive to the diuretic and electrolyte effects.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides (caution, cross-reactivity is possible but uncommon)
* Severe electrolyte depletion (e.g., hypokalemia, hyponatremia)
## Adverse Effects
* Electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia)
* Dehydration
* Hypotension
* Dizziness, lightheadedness
* Ototoxicity (especially with rapid IV administration or high doses)
* Hyperuricemia (can precipitate gout)
* Hyperglycemia
* Increased LDL, decreased HDL
* Rash, photosensitivity
## Key Drug Interactions
* **Aminoglycosides/Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **Antihypertensives:** Additive hypotensive effect.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects.
* **Lithium:** Reduced renal clearance of lithium, increasing risk of lithium toxicity.
* **Potassium-Sparing Diuretics (e.g., spironolactone):** Can be used to counteract potassium loss, but monitor electrolytes closely.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Fluid balance (intake/output, daily weights)
* Blood pressure
* Auditory assessment (especially with high doses or rapid IV infusion)
* Blood glucose (in diabetic patients)
* Uric acid (in patients prone to gout)
## Clinical Pearls
* Furosemide is a potent diuretic; initiating therapy at the lowest effective dose is recommended.
* Oral administration is generally preferred. For rapid diuresis or if oral route is not feasible, IV administration can be used, but monitor for hypotension and ototoxicity.
* Timing of dosing can impact patient comfort (e.g., avoid late-day dosing to minimize nocturia).
* Close monitoring of electrolytes is crucial to prevent serious complications, particularly hypokalemia.
* Patients with heart failure may require higher doses than those with renal or hepatic disease. Dosing for refractory edema can be complex and requires careful titration and monitoring.
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*Disclaimer: This information is intended for healthcare professionals and does not replace current prescribing information, institutional protocols, or clinical judgment. Always consult the most recent product labeling and relevant guidelines before making therapeutic decisions.*
