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# Furosemide
## Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver disease, and renal disease, including in patients with nephrotic syndrome. It is also used to manage hypertension, although it is not typically a first-line agent.
## Primary Indications
* Edema due to heart failure, liver cirrhosis, or renal disease.
* Hypertension (often in combination therapy).
## Adult Dosing
* **Edema:**
* Initial dose: 20-80 mg orally once daily.
* Subsequent doses: May be increased by 20-40 mg every 6-8 hours until desired response is achieved.
* Maintenance dose: Usually between 40-120 mg orally per day, but can range higher. Doses above 80 mg may be less effective and increase side effects.
* Intermittent dosing: For patients requiring higher doses, administering every other day or for 2-4 consecutive days with a rest day can be considered to minimize electrolyte depletion.
* Maximum dose: Typically 600 mg orally per day, though higher doses have been used under strict supervision.
* **Hypertension:**
* Initial dose: 40 mg orally twice daily.
* Maintenance dose: Adjust based on response.
* Maximum dose: Not well-established for hypertension, but generally lower doses are used compared to edema.
## Pediatric Dosing
* **Edema:**
* Initial dose: 1-2 mg/kg orally once daily.
* Subsequent doses: May be increased by 1-2 mg/kg every 6-8 hours until desired response.
* Maintenance dose: 1-4 mg/kg orally once daily, or divided twice daily.
* Maximum dose: 6 mg/kg orally per day.
* Intravenous: 1 mg/kg per dose, may be repeated every 2 hours as needed. Maximum IV dose: 6 mg/kg per dose.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be adjusted based on the degree of renal impairment and patient response. In severe renal failure, response may be diminished, and higher doses may be required, but this increases the risk of ototoxicity.
* **Hepatic Impairment:** Caution is advised; dose adjustments may be necessary.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides (cross-sensitivity may occur).
* Severe electrolyte depletion (e.g., hypokalemia, hyponatremia).
* Hepatic coma or severe degree of hepatic encephalopathy.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, orthostatic hypotension, hypokalemia, hyponatremia, hypochloremia, dehydration, increased urination, hyperuricemia, hyperglycemia.
* **Serious:** Ototoxicity (especially with rapid IV administration or high doses), severe electrolyte imbalances, pancreatitis, Stevens-Johnson syndrome, toxic epidermal necrolysis, aplastic anemia, agranulocytosis, thrombocytopenia, hyponatremia, kidney injury.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects of furosemide.
* **ACE Inhibitors/ARBs:** Increased risk of hyperkalemia and hypotension.
* **Lithium:** Reduced renal clearance of lithium, increasing the risk of lithium toxicity.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Corticosteroids:** Additive hypokalemia risk.
* **Probenecid:** May decrease the efficacy of furosemide.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Blood pressure (especially with ambulation)
* Urine output
* Hearing (especially with high doses or rapid IV administration)
* Blood glucose in diabetic patients
## Clinical Pearls
* Administer oral furosemide preferably on an empty stomach to enhance absorption, but if gastrointestinal upset occurs, it can be taken with food or milk.
* Rapid intravenous administration (e.g., over less than 30 seconds) can cause ototoxicity. Administer IV furosemide slowly, typically over 1-2 minutes, or as an infusion for higher doses.
* Monitor for signs of dehydration and electrolyte imbalance, especially in elderly patients or those with significant fluid losses.
* Consider potassium supplementation or a potassium-sparing diuretic if hypokalemia is persistent or symptomatic, but this requires careful monitoring.
* Edema may recur rapidly after stopping furosemide; lifestyle modifications and other therapies should be optimized.
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*This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions. Dosing and recommendations may vary based on patient-specific factors and local protocols.*
