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# Furosemide
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) associated with heart failure, liver disease, and kidney disease. It is also used to manage hypertension, though it is not typically a first-line agent for this indication.
## Primary Indications
* Edema due to congestive heart failure
* Edema due to liver cirrhosis
* Edema due to renal disease, including nephrotic syndrome
* Hypertension (adjunctive therapy)
## Adult Dosing
* **Edema:** Oral: 20-80 mg once daily. Higher doses may be given, up to 600 mg/day in severe cases, often divided. IV/IM: 20-40 mg once daily. May increase dose by 20 mg every 2 hours or by 40 mg every 4 hours. Usual IV dose range is 20-80 mg, but may be higher in acutely decompensated heart failure or severe renal impairment.
* **Hypertension:** Oral: 40 mg twice daily.
## Pediatric Dosing
* **Edema:** Oral: 1-2 mg/kg/dose once daily. If inadequate response, dose may be increased by 1-2 mg/kg/dose every 6-8 hours. Maximum dose: 6 mg/kg/day. IV/IM: 1 mg/kg/dose once daily. If inadequate response, dose may be increased by 1 mg/kg/dose every 2 hours. Maximum dose: 6 mg/kg/day.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased, especially with IV administration, as furosemide is renally eliminated. In severe renal impairment, the half-life is prolonged. Monitor electrolytes and fluid status closely.
* **Hepatic Impairment:** Reduced protein binding may increase the free drug concentration, requiring caution and potential dose reduction. Monitor electrolytes and fluid status closely.
## Contraindications
* Anuria
* History of hypersensitivity to furosemide or sulfonamides (potential for cross-sensitivity)
## Adverse Effects
* **Common:** Dizziness, lightheadedness, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypocalcemia, hypomagnesemia), dehydration, hypotension, hyperuricemia (can precipitate gout).
* **Serious:** Ototoxicity (hearing loss, tinnitus, especially with rapid IV administration or high doses), severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis), metabolic alkalosis, hyperglycemia, pancreatitis, blood dyscrasias.
## Key Drug Interactions
* **Aminoglycosides & Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **ACE Inhibitors & ARBs:** Increased risk of hypotension and renal dysfunction.
* **NSAIDs:** May reduce diuretic and antihypertensive effects, and increase risk of renal impairment.
* **Digoxin:** Risk of digoxin toxicity is increased with furosemide-induced hypokalemia or hypomagnesemia.
* **Lithium:** Furosemide can decrease lithium clearance, increasing lithium levels and toxicity risk.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (serum sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Fluid balance (intake/output, daily weights)
* Blood pressure
* Blood glucose (especially in diabetics)
* Uric acid
* Hearing (assess for tinnitus or hearing loss)
## Clinical Pearls
* Furosemide's onset of action is rapid, typically within 1 hour orally and within minutes IV/IM.
* Diuresis can last 4-6 hours orally and 2 hours IV/IM.
* Administering IV furosemide at a rate no faster than 20 mg/minute can reduce the risk of ototoxicity.
* Oral doses are usually given once daily in the morning to minimize nocturia. If a second dose is needed, it should be given no later than mid-afternoon.
* Dosing for heart failure is often guided by response (e.g., symptom improvement, weight loss) and may be significantly higher than standard doses. Continuous IV infusion may be considered in refractory edema.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the current prescribing information and your institution's protocols for complete and up-to-date guidance.*
