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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used for the management of edema associated with heart failure, cirrhosis, and renal disease, including the nephrotic syndrome. It is also used to treat hypertension.
## Primary Indications
* Edema due to heart failure, cirrhosis, or renal disease.
* Hypertension (adjunctive therapy).
## Adult Dosing
* **Edema:**
* **Oral:** 20 mg to 80 mg once daily. Can be increased by 20 mg to 40 mg every 6 to 8 hours as needed. May be administered as a single dose or divided doses.
* **IV/IM:** 20 mg to 40 mg once daily. Can be increased by 20 mg every 2 hours as needed. May be administered as a single dose or divided doses.
* **Maximum oral dose:** 600 mg/day (higher doses may be used in rare cases under close supervision).
* **Maximum IV/IM dose:** Typically 80-100 mg per dose; higher doses may be used in specific situations under continuous monitoring. Intermittent IV infusion may be preferred for doses > 80 mg. Continuous IV infusion may be considered for refractory edema.
* **Hypertension:**
* **Oral:** 40 mg twice daily.
* **Note:** Not typically a first-line agent for hypertension.
## Pediatric Dosing
* **Edema:**
* **Oral:** 1 mg/kg/dose to 2 mg/kg/dose every 6 to 12 hours.
* **IV/IM:** 1 mg/kg/dose every 6 to 12 hours.
* **Maximum dose:** 6 mg/kg/day (oral or IV/IM). Higher doses may be used in specific clinical situations with careful monitoring.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with renal impairment to achieve the same diuretic effect, but caution is advised due to potential for accumulation. Intermittent bolus dosing may be less effective than continuous infusion in severe renal impairment.
* **Hepatic Impairment:** Caution is advised. May require dose reduction.
## Contraindications
* Anuria.
* Hypersensitivity to furosemide or sulfonamides.
* Severe electrolyte depletion (e.g., hypokalemia, hyponatremia).
## Adverse Effects
* **Common:** Dizziness, lightheadedness, headache, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia), dehydration, hypotension, rash.
* **Serious:** Ototoxicity (especially with rapid IV administration or high doses), severe allergic reactions, hypovolemia, hyperglycemia, hyperuricemia (gout), pancreatitis, aplastic anemia, thrombocytopenia.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May reduce furosemide's diuretic and antihypertensive effects and increase the risk of renal impairment.
* **Lithium:** Furosemide can reduce renal clearance of lithium, increasing the risk of lithium toxicity.
* **Antihypertensives:** Additive hypotensive effect.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Fluid balance (intake and output).
* Renal function (BUN, creatinine).
* Blood pressure.
* Blood glucose (especially in diabetics).
* Uric acid.
* Hearing (especially with high doses or risk factors for ototoxicity).
## Clinical Pearls
* Administer oral furosemide with food or milk to minimize gastrointestinal upset.
* Rapid IV administration (e.g., > 4 mg/min) can increase the risk of ototoxicity. Infuse IV doses slowly or consider continuous infusion.
* Dosing for edema is highly individualized and should be titrated to the desired clinical response while monitoring for adverse effects.
* Consider the "crash and rebound" effect with once-daily dosing; a divided or continuous dosing regimen may be more effective for refractory edema.
* Patients with significant edema may require higher doses than those with mild edema or hypertension.
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*This information is intended for educational purposes and does not substitute for professional medical advice. Always consult the most current prescribing information and a qualified healthcare provider for diagnosis and treatment.*
