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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used for the management of edema associated with heart failure, liver cirrhosis, and renal disease, including the nephrotic syndrome. It is also used to treat hypertension, although it is not a first-line agent.
## Primary Indications
* Edema associated with congestive heart failure (CHF), liver cirrhosis, and renal disease.
* Hypertension (as adjunctive therapy).
## Adult Dosing
* **Edema:** Oral: 20-80 mg once daily. Doses may be increased by 20-40 mg every 6-8 hours as needed. Usual maintenance dose is 40-80 mg once daily. Intravenous (IV): 20-40 mg once daily. If inadequate response, doses may be increased by 20 mg every 2 hours. IV infusion: 10 mg/hour.
* **Hypertension:** Oral: 40 mg twice daily.
*Maximum oral dose is generally considered 600 mg daily, though higher doses have been used in refractory edema under close medical supervision.*
*Maximum IV dose is generally considered 400 mg daily, though higher doses have been used in refractory edema under close medical supervision.*
## Pediatric Dosing
* **Edema:** Oral: 1-2 mg/kg/dose once daily. May increase by 1-2 mg/kg/dose every 6-8 hours. Do not exceed 6 mg/kg/dose.
* **IV:** 1 mg/kg/dose once daily. May increase by 1 mg/kg/dose every 2 hours. Do not exceed 6 mg/kg/dose.
* **Infants < 30 days:** Generally avoid IV unless critically needed due to risk of ototoxicity.
## Dose Adjustments
* **Renal Impairment:** Furosemide is renally excreted. Dosing may need to be increased in patients with renal impairment to achieve the desired diuresis. However, higher doses may also increase the risk of ototoxicity.
* **Hepatic Impairment:** Use with caution. Monitor for electrolyte imbalances and hepatic encephalopathy.
## Contraindications
* Anuria.
* Hypersensitivity to furosemide or sulfonamides.
* History of severe hypersensitivity to thiazide diuretics.
## Adverse Effects
* **Electrolyte Imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration:** Dizziness, lightheadedness, hypotension.
* **Ototoxicity:** Hearing loss, tinnitus (especially with rapid IV administration or high doses).
* **Hyperglycemia.**
* **Hyperuricemia:** Can precipitate gout.
* **Dermatologic:** Rash, photosensitivity.
* **Gastrointestinal:** Nausea, vomiting, diarrhea.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Decreased lithium clearance, increasing lithium levels and risk of toxicity.
* **NSAIDs:** May blunt the diuretic and antihypertensive effect of furosemide.
* **Antihypertensives:** Additive hypotensive effects.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Serum electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Renal function (BUN, creatinine).
* Fluid status (intake/output, weight).
* Blood pressure.
* Hearing (especially with high doses or rapid IV administration).
* Blood glucose (in diabetic patients).
* Uric acid levels.
## Clinical Pearls
* Furosemide is a potent diuretic; onset of action is rapid (oral: 30-60 minutes; IV: 5 minutes).
* Administer IV furosemide slowly to minimize ototoxicity risk.
* Oral administration is generally preferred for chronic management of edema.
* Diuresis can lead to significant electrolyte depletion. Close monitoring is essential, particularly for potassium. Potassium supplementation or potassium-sparing diuretics may be necessary.
* May be given at a lower dose once daily to manage chronic edema, which can be more convenient and may reduce electrolyte losses compared to multiple daily doses.
* For continuous diuresis in hospitalized patients, IV infusion is preferred over intermittent boluses.
* Consider the potential for hypokalemia when co-administering with digoxin or other drugs that prolong the QT interval.
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*This information is for educational purposes only and does not substitute for professional medical advice. Always consult with a qualified healthcare provider to determine the best course of treatment for any medical condition. Please refer to the official prescribing information for the most up-to-date and complete drug details.*
