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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) associated with heart failure, liver disease, and kidney disease, including nephrotic syndrome. It is also used to treat high blood pressure, often in combination with other antihypertensives.
## Primary Indications
* Edema due to heart failure, liver cirrhosis, and renal disease.
* Hypertension.
## Adult Dosing
* **Edema:**
* **Initial:** 20-80 mg orally once daily. Doses may be given in the morning or divided.
* **Maintenance:** Adjust dose based on response. Doses may range from 20 mg every other day to 60-80 mg orally twice daily.
* **Maximum:** Generally 600 mg orally per day, but higher doses may be used under close supervision in specific situations (e.g., refractory edema).
* **Hypertension:**
* **Initial:** 40 mg orally twice daily.
* **Maintenance:** Adjust dose based on response. Doses may range from 80-120 mg orally per day divided into two doses.
* **Maximum:** Generally 120 mg orally per day, but higher doses may be used in resistant hypertension.
* **Intravenous (IV) Dosing for Edema:**
* **Initial:** 20-40 mg IV once daily.
* **Subsequent Doses:** May be given every 6-8 hours as needed. The total daily dose may be increased by 20-40 mg increments until desired diuresis is achieved.
* **Maximum:** Generally 600 mg IV per day, but higher doses may be used under close supervision.
## Pediatric Dosing
* **Edema and Hypertension:**
* **Oral:** 1-2 mg/kg/dose orally once or twice daily.
* **Maximum Oral Dose:** 6 mg/kg/dose (not to exceed 40 mg/dose if under 1 year, or 80 mg/dose if over 1 year).
* **Intravenous (IV):** 1 mg/kg/dose IV once or twice daily.
* **Maximum IV Dose:** 1 mg/kg/dose (not to exceed 20 mg/dose in neonates or infants up to 2 months of age, or 40 mg/dose in infants older than 2 months).
* *Note: Dosing and frequency may vary based on local protocol and clinical response.*
## Dose Adjustments
* **Renal Impairment:** May require higher doses due to reduced kidney function and impaired absorption. Monitor electrolytes and renal function closely.
* **Hepatic Impairment:** May require lower doses due to increased bioavailability. Monitor electrolytes and fluid balance closely.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Electrolyte Imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and Hypotension.**
* **Ototoxicity:** Transient or permanent hearing loss, especially with rapid IV administration or high doses.
* **Hyperglycemia.**
* **Hyperuricemia** (can precipitate gout).
* **Increased BUN and Creatinine.**
* **Photosensitivity.**
* **Aplastic anemia, agranulocytosis, thrombocytopenia, neutropenia** (rare).
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Antihypertensives (including ACE inhibitors, ARBs, beta-blockers):** Additive hypotensive effect.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Increased risk of lithium toxicity due to decreased renal clearance.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects of furosemide.
* **Potassium-Sparing Diuretics (e.g., spironolactone, amiloride):** May counteract potassium loss.
## Monitoring
* Serum electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Renal function (BUN, creatinine).
* Blood pressure.
* Urine output.
* Hearing (especially with high doses or IV administration).
* Blood glucose (in diabetic patients).
* Uric acid (in patients with history of gout).
## Clinical Pearls
* Administer oral furosemide in the morning to minimize nocturia.
* Rapid IV administration can increase the risk of ototoxicity. Infuse slowly, typically over 30-60 minutes.
* Monitor for signs and symptoms of hypokalemia (muscle cramps, weakness, arrhythmias). Potassium supplementation may be necessary.
* In patients with heart failure, furosemide is often titrated to achieve a target weight loss or symptom relief, rather than a specific dose.
* Be cautious when co-administering with other ototoxic or nephrotoxic drugs.
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*Please verify current prescribing information for the most up-to-date details on dosage, indications, contraindications, and warnings.*
