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# Furosemide (Lasix)
## Overview
Furosemide is a loop diuretic used to treat fluid overload (edema) associated with heart failure, liver disease, and kidney disease, including nephrotic syndrome. It is also used to treat high blood pressure, usually in combination with other antihypertensives.
## Primary Indications
* Edema due to heart failure, liver cirrhosis, and renal disease.
* Hypertension.
## Adult Dosing
* **Edema:**
* Oral: Initial dose is typically 20-80 mg once or twice daily. Doses may be increased by 20-40 mg every 6-8 hours as needed. Usual maintenance dose is 40-80 mg once or twice daily.
* Intravenous (IV)/Intramuscular (IM): Initial dose is typically 20-40 mg once. If insufficient response, subsequent doses of 20-40 mg may be given every 2 hours. Higher doses may be required for severe edema.
* Maximum oral dose: 600 mg/day (though higher doses may be used in rare, supervised cases).
* Maximum IV/IM dose: Generally not to exceed 200 mg in a single dose, but higher doses may be used in specific situations under close monitoring.
* **Hypertension:**
* Oral: Initial dose is typically 40 mg twice daily. Maintenance doses usually range from 20-120 mg/day divided into two doses.
* It is generally not recommended as a sole agent for hypertension.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose every 6 hours. May increase by 1-2 mg/kg/dose every 6 hours if needed.
* IV/IM: 1 mg/kg/dose every 6 hours. May increase by 1 mg/kg/dose every 6 hours if needed.
* Maximum dose: 6 mg/kg/day for oral, and 1 mg/kg/dose or 40 mg/dose (whichever is less) for IV/IM.
* **Neonatal Edema:** Dosing can be highly variable and requires careful titration. Consult specific neonatal guidelines.
## Dose Adjustments
* **Renal Impairment:** Dosage may need to be increased in renal insufficiency, but monitor electrolytes and fluid status closely. In severe renal impairment, continuous IV infusion may be more effective than intermittent boluses.
* **Hepatic Impairment:** Caution is advised, as liver disease can alter furosemide metabolism and response. Monitor for electrolyte imbalances and hepatic encephalopathy.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), dehydration, hypotension, hyperglycemia.
* **Less Common:** Ototoxicity (especially with rapid IV administration or high doses), hyperuricemia, rash, Stevens-Johnson syndrome, aplastic anemia.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity.
* **Other Ototoxic Drugs:** Increased risk of hearing damage.
* **ACE Inhibitors/ARBs/Diuretics:** Additive hypotensive effect and increased risk of electrolyte imbalances.
* **NSAIDs:** May decrease diuretic and antihypertensive effect; increased risk of renal dysfunction.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, increasing lithium toxicity risk.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Renal function (BUN, creatinine).
* Fluid balance (intake and output, daily weights).
* Blood pressure.
* Blood glucose (especially in diabetics).
* Hearing (if experiencing symptoms of ototoxicity).
## Clinical Pearls
* Administer oral furosemide on an empty stomach to increase absorption; however, may be taken with food or milk if gastric upset occurs.
* IV administration should be given slowly (over at least 30-60 minutes) to reduce the risk of ototoxicity. Avoid concurrent administration with other potentially ototoxic drugs in the same IV line.
* Rapid IV administration can lead to transient hearing loss.
* Oral absorption can be erratic in patients with severe edema. IV therapy may be necessary.
* Monitor for signs of dehydration and electrolyte depletion, particularly hypokalemia, which can predispose to arrhythmias. Potassium supplementation or potassium-sparing diuretics may be needed.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the current prescribing information and relevant clinical guidelines before making therapeutic decisions. Dosing may vary based on individual patient factors and local protocols.*
