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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) and high blood pressure. It works by inhibiting the Na-K-2Cl symporter in the thick ascending limb of the Loop of Henle, leading to increased excretion of sodium, potassium, chloride, and water.
## Primary Indications
* Edema associated with congestive heart failure (CHF), cirrhosis of the liver, and renal disease (including nephrotic syndrome).
* Hypertension, usually in combination with other antihypertensives.
* Acute pulmonary edema.
## Adult Dosing
* **Edema:** Oral: Typically starts at 20-80 mg once or twice daily. Doses can be increased by 20-40 mg every 6-8 hours as needed. Usual maintenance dose is 40-80 mg daily. Maximum oral dose is generally 600 mg/day, but may be higher in refractory cases under close supervision. IV/IM: Typically starts at 20-40 mg once or twice daily. If no response, doses can be increased by 20 mg every 2 hours. Maximum IV/IM dose is typically 200 mg as a single dose, but higher doses may be used in refractory edema under careful monitoring.
* **Hypertension:** Oral: Typically 40 mg twice daily. Usually used in combination therapy.
* **Acute Pulmonary Edema:** IV: Typically 20-40 mg given as a bolus. If inadequate response, can be repeated every 2 hours. Higher doses (e.g., 80-120 mg) may be used in severe cases.
*Specific dosing strategies, especially for IV administration and continuous infusions, may vary based on local protocols and patient response.*
## Pediatric Dosing
* **Edema:** Oral: 1-4 mg/kg/day divided into 1-2 doses. Maximum: 6 mg/kg/day. IV/IM: 1 mg/kg/dose every 6-12 hours. Maximum: 6 mg/kg/dose.
* **Neonates:** Oral: 1 mg/kg/dose every 12-24 hours. IV/IM: 0.5-1 mg/kg/dose every 12-24 hours.
*Dosing in neonates and infants requires careful monitoring due to immature renal function.*
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with renal insufficiency to achieve the same diuretic effect. Monitor for toxicity.
* **Hepatic Impairment:** Use with caution. Dose may need to be adjusted due to altered protein binding and metabolism.
## Contraindications
* Anuria.
* History of hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Electrolyte imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and hypotension.**
* **Ototoxicity** (especially with rapid IV administration or high doses).
* **Hyperuricemia** (can precipitate gout).
* **Hyperglycemia.**
* **Dizziness, headache.**
* **Rash, photosensitivity.**
* **Aplastic anemia, thrombocytopenia, agranulocytosis** (rare).
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Other ototoxic drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects of furosemide.
* **Lithium:** May decrease lithium clearance, increasing the risk of lithium toxicity.
* **Antihypertensives:** Additive hypotensive effects.
* **Digoxin:** Risk of digoxin toxicity is increased with furosemide-induced hypokalemia.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* **Electrolytes:** Serum electrolytes (Na, K, Cl, Mg, Ca) and BUN/creatinine at baseline and regularly during treatment.
* **Fluid balance:** Daily weights, intake and output.
* **Blood pressure.**
* **Auditory function** (especially with high doses or risk factors).
## Clinical Pearls
* Administer orally administered furosemide on an empty stomach to increase absorption, but may be given with food or milk if gastric irritation occurs.
* IV administration should be slow (e.g., over 30-60 minutes) to minimize ototoxicity and hypotension. Avoid rapid injection.
* Monitor for signs and symptoms of electrolyte imbalances, especially hypokalemia, which can lead to arrhythmias. Potassium supplementation may be necessary.
* In patients with significant edema, daily weights are the most reliable indicator of fluid loss.
* Furosemide can exacerbate Systemic Lupus Erythematosus (SLE).
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and your healthcare provider for any questions or before making any decisions related to drug therapy.
