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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium and chloride in the ascending limb of the loop of Henle, leading to increased excretion of water, sodium, potassium, chloride, calcium, and magnesium.
## Primary Indications
* **Edema** associated with congestive heart failure, liver cirrhosis, and renal disease (including the nephrotic syndrome).
* **Hypertension**, usually in combination with other antihypertensives.
## Adult Dosing
* **Edema:**
* **Oral:** Initial dose is typically 20-80 mg once daily. Doses may be increased by 20-40 mg every 6-8 hours as needed. Doses can range from 20 mg to 600 mg daily, divided into 1-4 doses. The lowest effective dose should be used.
* **Intravenous (IV) / Intramuscular (IM):** Initial dose is typically 20-40 mg once daily. If inadequate response, doses can be increased by 20 mg every 2 hours. Doses can range from 20 mg to 600 mg daily. For severe edema or rapid diuresis, continuous IV infusion may be used, starting at 10 mg/hour after an initial IV bolus of 20-40 mg.
* **Hypertension:**
* **Oral:** Initial dose is typically 40 mg twice daily. May be adjusted to 80-120 mg daily in divided doses. Often used in combination with other antihypertensives.
## Pediatric Dosing
Dosing in pediatric patients is highly individualized and depends on the underlying condition and clinical response. Local protocol is essential for determining precise dosing.
* **Edema:**
* **Oral:** Typically 1-4 mg/kg/day divided into 1-4 doses. Maximum dose is usually 6 mg/kg/day.
* **Intravenous (IV) / Intramuscular (IM):** Typically 1 mg/kg/dose. Doses can be repeated every 6 hours if needed. Maximum single dose is usually 6 mg/kg.
* **Neonatal hyperbilirubinemia:** May be used in specific cases, but not a primary indication.
## Dose Adjustments
* **Renal Impairment:** Dose adjustments are often necessary. In severe renal impairment, higher doses may be required to achieve a diuretic effect, but caution is advised.
* **Hepatic Impairment:** Lower doses may be necessary due to altered drug metabolism and increased sensitivity to fluid and electrolyte imbalances.
## Contraindications
* Anuria.
* Hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Electrolyte Imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and Hypotension:** Especially with rapid diuresis.
* **Ototoxicity:** Hearing impairment, tinnitus, vertigo (more common with rapid IV administration or high doses).
* **Metabolic Effects:** Hyperuricemia, hyperglycemia, increased cholesterol and triglyceride levels.
* **Gastrointestinal:** Nausea, vomiting, diarrhea, constipation.
* **Dermatologic:** Rash, photosensitivity.
* **Hematologic:** Agranulocytosis, thrombocytopenia, aplastic anemia (rare).
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May blunt the diuretic and antihypertensive effects of furosemide and increase the risk of renal dysfunction.
* **Lithium:** Furosemide can decrease lithium clearance, increasing lithium toxicity risk.
* **Antihypertensives:** Additive hypotensive effect.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity if hypokalemia occurs.
## Monitoring
* **Electrolytes:** Sodium, potassium, chloride, magnesium, calcium.
* **Renal Function:** Serum creatinine, BUN.
* **Fluid Balance:** Intake and output, weight.
* **Blood Pressure:** Especially in patients treated for hypertension.
* **Hearing:** Monitor for tinnitus or hearing loss.
## Clinical Pearls
* Administer oral furosemide in the morning to minimize nocturia.
* Rapid IV administration can increase the risk of ototoxicity. Slow infusion or intermittent dosing is preferred.
* Monitor electrolytes closely, particularly potassium. Potassium supplementation may be necessary.
* Furosemide can potentiate the effects of other antihypertensive agents.
* Patients with sulfonamide allergies may have a cross-sensitivity reaction, although this is debated and less common than with other sulfonamide drugs.
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**Disclaimer:** This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and local protocols for definitive guidance on drug use.
