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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) associated with conditions such as heart failure, liver disease, and kidney disease. It also treats high blood pressure, usually in combination with other antihypertensives.
## Primary Indications
* Edema due to heart failure, liver cirrhosis, and renal disease.
* Hypertension (often in combination therapy).
## Adult Dosing
* **Edema:**
* Initial: 20-80 mg orally once or twice daily.
* Further doses can be adjusted by 20-40 mg at intervals of 6-8 hours.
* Maximum daily dose: 600 mg orally.
* For severe edema, higher doses may be required under close supervision.
* **Hypertension:**
* Initial: 40 mg orally twice daily.
* Maintenance: Adjust dose as needed.
* Maximum daily dose: 400 mg orally.
* **Intravenous (IV) administration (for more rapid onset or when oral route is not feasible):**
* Edema: 20-40 mg IV every 6-12 hours. If no response after 2 hours, the dose can be doubled.
* Continuous IV infusion: 4 mg/hour after an initial bolus dose of 20-40 mg.
* Maximum IV dose: Typically 200 mg in a single dose, but higher doses may be used in specific situations under close monitoring.
## Pediatric Dosing
* **Edema:**
* Infants and children: 1-2 mg/kg orally every 6-12 hours.
* Maximum daily oral dose: 6 mg/kg.
* IV/IM: 1 mg/kg every 6-12 hours.
* Maximum IV/IM dose: 20 mg per dose.
* For premature infants, specific dosing guidelines may vary.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased due to decreased GFR. However, very high doses can be ototoxic. Monitor efficacy and toxicity closely.
* **Hepatic Impairment:** Caution is advised. Electrolyte imbalances can precipitate hepatic encephalopathy.
## Contraindications
* Anuria.
* History of hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia), dehydration, hypotension.
* **Serious:** Ototoxicity (hearing loss, tinnitus, often reversible but can be permanent with high doses or rapid IV administration), severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis), pancreatitis, blood dyscrasias, hyperglycemia.
## Key Drug Interactions
* **Aminoglycosides, other ototoxic drugs:** Increased risk of ototoxicity.
* **ACE inhibitors, ARBs, NSAIDs:** Increased risk of renal impairment and hyperkalemia. NSAIDs can also reduce the diuretic effect.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, increasing lithium toxicity risk.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride)
* Renal function (BUN, creatinine)
* Blood pressure
* Fluid balance (intake and output, daily weights)
* Auditory function (especially with high doses or prolonged therapy)
## Clinical Pearls
* Furosemide is a potent diuretic; rapid diuresis can lead to dehydration and electrolyte depletion.
* Oral administration is preferred for chronic management of edema and hypertension.
* IV administration is indicated for patients with acute pulmonary edema, severe volume overload, or when oral absorption is compromised.
* To minimize nocturia, administer the last dose no later than 4-6 hours before bedtime.
* Hypokalemia is a common side effect. Patients may require potassium supplementation or a potassium-sparing diuretic.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the current prescribing information and relevant guidelines before making clinical decisions.*
