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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 reabsorption of sodium and chloride in the kidneys, leading to increased urine output.
## Primary Indications
* Edema associated with congestive heart failure (CHF), liver cirrhosis, and renal disease (including the nephrotic syndrome).
* Hypertension (used alone or in combination with other antihypertensives).
## Adult Dosing
* **Edema:** Oral doses typically range from 20 mg to 80 mg once daily. Higher doses may be given if needed, but generally not exceeding 600 mg/day without careful monitoring. Intravenous (IV) or intramuscular (IM) doses are often half the oral dose (e.g., 20 mg to 40 mg IV/IM). Dosing frequency may vary based on response.
* **Hypertension:** Oral doses typically start at 40 mg twice daily. Doses may be adjusted based on blood pressure response.
## Pediatric Dosing
* **Edema:** Oral: 1 mg/kg to 2 mg/kg per dose, administered once or twice daily. Maximum daily dose is generally 6 mg/kg. IV/IM: 1 mg/kg per dose, administered once or twice daily. Maximum IV/IM dose is generally 20 mg per dose. Dosing requires careful titration and monitoring.
## Dose Adjustments
* **Renal Impairment:** Higher doses may be required in patients with renal insufficiency due to reduced renal clearance. However, caution is advised, and monitoring for efficacy and toxicity is crucial.
* **Hepatic Impairment:** Use with caution. Dose adjustments may be necessary.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or its sulfonamide components.
* Hepatic coma or severe electrolyte depletion.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypocalcemia, hypomagnesemia), dehydration, hypotension, hyperglycemia.
* **Serious:** Ototoxicity (especially with rapid IV administration or in high doses), severe skin reactions (e.g., Stevens-Johnson syndrome), blood dyscrasias, pancreatitis, severe allergic reactions.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects of furosemide and increase the risk of renal impairment.
* **Lithium:** Furosemide can decrease lithium clearance, increasing serum lithium levels and the risk of toxicity.
* **Antihypertensives:** Additive hypotensive effects.
* **Digoxin:** Risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* **Electrolytes:** Monitor serum electrolytes (sodium, potassium, chloride, magnesium, calcium) regularly, especially with chronic use or in high-risk patients.
* **Renal Function:** Monitor serum creatinine and BUN.
* **Blood Pressure:** Monitor blood pressure, especially when used for hypertension or in patients prone to hypotension.
* **Urine Output:** Monitor fluid balance and urine output.
* **Hearing:** Assess for tinnitus or hearing loss, especially with high doses or rapid IV administration.
## Clinical Pearls
* Furosemide is a potent diuretic; initiate therapy at the lowest effective dose.
* Oral administration may be delayed in onset but provides a smoother diuresis compared to IV.
* Rapid IV administration (e.g., > 4 mg/minute) can increase the risk of ototoxicity.
* Electrolyte monitoring and replacement (especially potassium) are critical.
* Patients with renal insufficiency may require higher doses but are also at increased risk of toxicity.
* Concomitant administration with aminoglycosides requires extreme caution and careful monitoring.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and clinical guidelines for definitive dosing, safety, and management strategies. Local protocols may dictate specific dosing adjustments.
