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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium, chloride, and potassium in the ascending limb of the Loop of Henle.
## Primary Indications
* Edema associated with congestive heart failure, liver cirrhosis, and renal disease (including the nephrotic syndrome).
* Hypertension, usually used in combination with other antihypertensives.
* Acute pulmonary edema.
## Adult Dosing
* **Edema:** Typically initiated at 20-80 mg orally once or twice daily. Doses can be increased by 20-40 mg increments every 6-8 hours as needed. Maximum daily oral dose is generally 600 mg, though higher doses may be used in specific clinical scenarios under close monitoring.
* **Hypertension:** Typically 40 mg orally once or twice daily.
* **Acute Pulmonary Edema:** 20-40 mg intravenously. If no adequate diuresis occurs within 2 hours, may repeat with 40 mg IV.
## Pediatric Dosing
* **Edema:** 1-2 mg/kg/dose orally every 6-12 hours. Maximum dose 6 mg/kg/dose.
* **Edema (IV/IM):** 1 mg/kg/dose every 6-12 hours. Maximum dose 20 mg/dose per administration, or higher if needed for fluid overload under very close monitoring.
* **Neonates:** Lower doses may be required due to immature renal function. Generally 1 mg/kg/dose every 24-48 hours.
## Dose Adjustments
* **Renal Impairment:** Doses may need to be increased in renal insufficiency due to reduced drug elimination and impaired diuretic response. However, monitor closely for electrolyte imbalances and dehydration.
* **Hepatic Impairment:** Use with caution; dose adjustment may be necessary.
## Contraindications
* Anuria.
* History of hypersensitivity to furosemide or sulfonamides (potential for cross-sensitivity).
## Adverse Effects
* **Electrolyte Imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and Hypotension.**
* **Ototoxicity:** Especially with rapid IV administration or in patients with renal impairment, and when given with other ototoxic drugs.
* **Hyperglycemia.**
* **Hyperuricemia:** May precipitate gout.
* **Dizziness, lightheadedness.**
* **Rash, photosensitivity.**
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **Antihypertensives (including diuretics, ACE inhibitors, ARBs):** Additive hypotensive effect.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, increasing lithium toxicity risk.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects of furosemide.
* **Potassium supplements/Potassium-sparing diuretics:** May counteract hypokalemia, but caution still needed due to risk of hyperkalemia with potassium-sparing agents.
## Monitoring
* **Electrolytes:** Serum sodium, potassium, chloride, magnesium, calcium.
* **Renal Function:** Serum creatinine and BUN.
* **Fluid Status:** Daily weight, intake and output, signs of edema.
* **Blood Pressure.**
* **Blood Glucose.**
* **Uric Acid.**
* **Hearing:** Assess for tinnitus or hearing loss, particularly with high doses or in susceptible patients.
## Clinical Pearls
* Furosemide is a potent diuretic; rapid or excessive diuresis can lead to significant electrolyte and fluid depletion.
* Oral administration may be followed by a period of diuresis lasting 6-8 hours.
* Intravenous administration provides a more rapid onset of diuresis (within minutes).
* Administer IV furosemide slowly to minimize the risk of ototoxicity and hypotension.
* Monitor for signs of dehydration (dry mouth, thirst, reduced urine output, dizziness).
* Furosemide is a sulfonamide derivative; caution in patients with sulfonamide allergy.
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**Disclaimer:** This information is intended for educational purposes and does not substitute for professional medical advice. Always consult the most current prescribing information and your healthcare provider to ensure patient safety and optimal therapeutic outcomes.
