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# Furosemide (Lasix)
## Overview
Furosemide is a loop diuretic used to treat fluid overload and edema associated with heart failure, liver disease, and kidney disease. It also treats high blood pressure.
## Primary Indications
* Edema due to congestive heart failure, liver cirrhosis, and renal disease.
* Hypertension, usually in combination with other antihypertensives.
## Adult Dosing
* **Edema:**
* Initial dose: 20-80 mg PO once daily.
* Subsequent doses: May be given once daily, twice daily, or every day for 3-5 days with a rest day.
* Maximum dose: 600 mg PO daily (higher doses may be used in severe cases under close supervision).
* **Hypertension:**
* Initial dose: 40 mg PO twice daily.
* Maintenance dose: Adjust based on response.
* Maximum dose: Not well established for monotherapy; generally used adjunctively.
## Pediatric Dosing
Dosing varies significantly based on indication and patient weight. Exact dosing often depends on local protocol and clinical assessment.
* **Edema/Hypertension:**
* Premature infants: 0.5-1 mg/kg/dose PO every 12-24 hours.
* Term infants and children: 1-2 mg/kg/dose PO every 6-12 hours.
* Maximum dose: 6 mg/kg/day PO.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with renal impairment to achieve the same diuretic effect, but monitor closely for electrolyte imbalances and ototoxicity.
* **Hepatic Impairment:** Caution is advised; monitor for electrolyte imbalances and hepatic encephalopathy.
## Contraindications
* Anuria.
* Hypersensitivity to furosemide or sulfonamides.
* Severe electrolyte depletion (e.g., hypokalemia, hyponatremia).
## Adverse Effects
* **Electrolyte Abnormalities:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration:** Dizziness, lightheadedness.
* **Ototoxicity:** Tinnitus, hearing loss (especially with rapid IV administration or high doses).
* **Metabolic:** Hyperglycemia, hyperuricemia (may precipitate gout).
* **Renal:** Increased BUN and creatinine.
* **Gastrointestinal:** Nausea, vomiting, diarrhea.
* **Dermatologic:** Rash, photosensitivity.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **NSAIDs:** May reduce the diuretic and natriuretic effect of furosemide.
* **Lithium:** Increased risk of lithium toxicity due to decreased renal clearance.
* **Potassium-Sparing Diuretics/ACE Inhibitors/ARBs/Spironolactone:** Increased risk of hyperkalemia.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity if hypokalemia occurs.
## Monitoring
* **Electrolytes:** Sodium, potassium, chloride, magnesium, calcium.
* **Renal function:** BUN, creatinine.
* **Fluid status:** Daily weights, intake/output.
* **Blood pressure.**
* **Hearing:** Assess for tinnitus or hearing impairment, especially with high doses or IV administration.
* **Blood glucose and uric acid levels** in susceptible patients.
## Clinical Pearls
* Administer oral doses with food or milk to minimize gastrointestinal upset.
* Rapid IV administration can increase the risk of ototoxicity. Administer IV furosemide slowly, typically over 30-60 minutes.
* Monitor patients closely for signs of dehydration and electrolyte imbalances, particularly potassium levels, as hypokalemia can increase the risk of arrhythmias and digoxin toxicity.
* Furosemide can cause photosensitivity; advise patients to use sun protection.
* In patients with heart failure, consider the potential for worsening renal function due to aggressive diuresis.
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**Disclaimer:** This information is intended for healthcare professionals and does not replace comprehensive prescribing information. Always verify current prescribing information and consult with a qualified healthcare provider before making any treatment decisions.
