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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium, chloride, and potassium in the ascending limb of the loop of Henle, leading to increased excretion of these electrolytes and water.
## Primary Indications
* Edema associated with heart failure, liver cirrhosis, and renal disease (including the nephrotic syndrome).
* Hypertension (typically as adjunctive therapy).
* Acute pulmonary edema.
## Adult Dosing
* **Edema:** Oral: Initial dose is typically 20-80 mg once daily. Doses may be adjusted by 20-40 mg at intervals depending on response. Doses up to 200 mg once daily or divided twice daily can be used. Intravenous (IV): Initial dose is typically 20-40 mg once daily. Higher doses may be administered. The IV dose is generally about half the oral dose due to increased bioavailability.
* **Hypertension:** Oral: Doses typically range from 40 mg twice daily. Lower doses may be effective.
* **Acute Pulmonary Edema:** IV: 20-40 mg administered, may repeat or increase dose as needed.
## Pediatric Dosing
* **Edema/Hypertension:** Oral: 1-2 mg/kg/dose once daily, not to exceed 6 mg/kg/day. Intravenous (IV): 1 mg/kg/dose, not to exceed 20 mg per dose. Higher doses may be required in neonates and infants, and IV administration may be preferred for more predictable absorption. Dosing should be individualized.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with severe renal impairment due to impaired excretion. However, caution is advised as it can precipitate azotemia. In patients with renal failure, higher doses may be needed.
* **Hepatic Impairment:** Caution is advised. Dosing adjustments may be necessary due to altered drug metabolism and potential for electrolyte imbalances.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, weakness, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), dehydration, hypotension, hyperglycemia, hyperuricemia.
* **Less Common:** Ototoxicity (especially with rapid IV administration or in renal impairment), skin rash, photosensitivity, gastrointestinal upset, pancreatitis, blood dyscrasias.
## Key Drug Interactions
* **Aminoglycosides/Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **Corticosteroids/ACTH:** Increased risk of electrolyte depletion.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May reduce furosemide's diuretic and antihypertensive effects.
* **Antihypertensives:** Additive hypotensive effects.
* **Lithium:** Reduced lithium clearance, increasing the risk of lithium toxicity.
* **Sucralfate:** May reduce absorption of furosemide. Separate administration by at least 2 hours.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Renal function (BUN, creatinine).
* Blood pressure.
* Fluid balance (intake and output).
* Hearing (especially with high doses or in those with risk factors).
* Blood glucose (in diabetic patients).
* Uric acid.
## Clinical Pearls
* Oral absorption can be variable, especially in edematous states. IV administration may be preferred for rapid diuresis or when oral absorption is compromised.
* Rapid IV administration can lead to ototoxicity. Administer IV furosemide slowly (e.g., over 1-2 minutes for doses up to 40 mg).
* Monitor for signs and symptoms of dehydration and electrolyte imbalances closely.
* Potassium supplementation is often required when using furosemide, particularly with higher doses or prolonged use.
* Dosing for pediatric patients can be complex and should be individualized based on clinical response and weight.
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***Disclaimer:** This information is intended for educational purposes and does not substitute for professional medical advice. Always consult the current prescribing information and your healthcare provider for specific guidance regarding medication use.*
