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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used for the management of edema associated with heart failure, liver cirrhosis, and renal disease, including the nephrotic syndrome. It is also used to manage hypertension, either alone or in combination with other antihypertensives.
## Primary Indications
* Edema due to heart failure, liver disease, and renal disease.
* Hypertension.
* Acute pulmonary edema.
## Adult Dosing
* **Edema:**
* Initial dose: 20-80 mg orally once daily. Doses may be increased by 20-40 mg every 6-8 hours as needed.
* Maintenance dose: Titrated to the lowest effective dose, typically administered once or twice daily.
* Maximum daily oral dose: 600 mg.
* **Hypertension:**
* Initial dose: 40 mg orally twice daily.
* Maintenance dose: Adjusted as needed.
* Maximum daily oral dose: 600 mg.
* **Acute Pulmonary Edema:**
* Initial dose: 40 mg intravenously. If response is inadequate after 1-2 hours, an additional 40 mg IV may be administered.
* Subsequent doses: 20-120 mg intravenously every 2-4 hours as needed.
* Maximum dose: Generally not to exceed 600 mg in a 24-hour period, though higher doses may be used under close medical supervision in specific situations.
## Pediatric Dosing
* **Edema and Hypertension:**
* Initial dose: 1-2 mg/kg orally once daily.
* Maximum initial dose: 40 mg once daily.
* If response is inadequate, doses may be increased by 1-2 mg/kg orally every 6-8 hours.
* Maximum daily oral dose: 6 mg/kg, not to exceed 40 mg per day for infants and children up to 12 years of age.
* For children 12 years and older, the maximum daily oral dose is 600 mg.
* **Acute Pulmonary Edema:**
* Initial dose: 1 mg/kg intravenously, not to exceed 20 mg.
* If response is inadequate, additional doses of 1 mg/kg may be administered every 2-4 hours.
* For infants and children up to 12 years of age, the maximum single intravenous dose is 20 mg.
* For children 12 years and older, the maximum single intravenous dose is 40 mg.
## Dose Adjustments
* **Renal Impairment:** Furosemide clearance is dependent on renal function. Dose may need to be increased in renal impairment, or if there is significant fluid retention. However, higher doses may be less effective and more ototoxic. Dosing is highly individualized.
* **Hepatic Impairment:** Furosemide half-life may be prolonged. Monitor electrolytes and fluid status closely.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Electrolyte imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration:** Dizziness, lightheadedness, orthostatic hypotension.
* **Ototoxicity:** Hearing loss, tinnitus (especially with rapid IV administration or high doses).
* **Metabolic effects:** Hyperglycemia, hyperuricemia (gout).
* **Gastrointestinal:** Nausea, vomiting, diarrhea.
* **Hematologic:** Aplastic anemia, thrombocytopenia, agranulocytosis (rare).
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Antihypertensives:** Additive hypotensive effects.
* **NSAIDs:** May reduce diuretic and antihypertensive effect; increased risk of nephrotoxicity.
* **Lithium:** Furosemide can decrease lithium clearance, increasing lithium toxicity risk.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Hypokalemia induced by furosemide increases risk of digoxin toxicity.
## Monitoring
* Serum electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Renal function (BUN, creatinine).
* Fluid balance (intake and output, daily weights).
* Blood pressure.
* Blood glucose (especially in diabetic patients).
* Uric acid.
* Hearing function with high doses or prolonged therapy.
## Clinical Pearls
* Furosemide is a potent diuretic; monitor for signs of dehydration and electrolyte depletion.
* Administer IV furosemide slowly (e.g., over 30-60 minutes) to minimize ototoxicity risk. Rapid IV administration can lead to tinnitus and hearing loss.
* The oral and intravenous doses are not equivalent. IV doses are generally about half of the equivalent oral dose.
* Tolerance to the diuretic effect may occur with chronic use.
* Furosemide can precipitate or exacerbate gout due to hyperuricemia.
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*This information is intended for educational purposes and does not substitute for professional medical advice. Always consult the current prescribing information and a qualified healthcare provider for any medical decisions.*
