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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver cirrhosis, and renal disease, including nephrotic syndrome. It is also used to manage hypertension, usually in combination with other antihypertensives.
## Primary Indications
* Edema secondary to heart failure, liver cirrhosis, and renal disease.
* Hypertension.
## Adult Dosing
* **Edema:**
* **Oral:** Initial dose of 20-80 mg once daily. If needed, doses can be increased by 20-40 mg every 6-8 hours, or the dose can be divided and given twice daily. Typical maintenance doses range from 20-80 mg daily. Maximum oral dose is 600 mg daily, but higher doses may be used in rare cases under close monitoring.
* **Intravenous (IV) or Intramuscular (IM):** Initial dose of 20-40 mg once daily. If response is inadequate, doses can be increased by 20 mg every 2 hours. Maximum IV/IM dose is generally 200 mg in a single dose, but higher doses may be required in severe cases with continuous infusion or divided doses.
* **Hypertension:**
* **Oral:** Initial dose of 40 mg twice daily. This is usually used in combination with other antihypertensives.
## Pediatric Dosing
* **Edema:**
* **Oral:** 1-2 mg/kg/dose once daily. If inadequate response, increase to 3 mg/kg/dose once daily. For chronic use, the dose can be divided and given twice daily. Maximum oral dose: 6 mg/kg/dose.
* **IV/IM:** 1 mg/kg/dose once daily. If inadequate response, increase to 2 mg/kg/dose once daily. Maximum IV/IM dose: 2 mg/kg/dose.
* **Note:** Dosing for neonates and premature infants can be variable due to immature renal function.
## Dose Adjustments
* **Renal Impairment:** Patients with severe renal impairment may require lower doses or less frequent administration. Higher doses may be needed in some cases to achieve diuresis, especially in the presence of edema and hypoalbuminemia.
* **Hepatic Impairment:** Caution is advised; dose reduction may be necessary.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides (potential for cross-sensitivity).
* Severe electrolyte depletion (e.g., hypokalemia, hyponatremia).
* Hepatic coma or severe degrees of diarrhea.
## Adverse Effects
* **Electrolyte imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and hypotension.**
* **Ototoxicity:** Hearing loss, tinnitus (especially with rapid IV administration or high doses).
* **Metabolic:** Hyperuricemia, hyperglycemia.
* **Renal:** Increased BUN and creatinine.
* **Gastrointestinal:** Nausea, vomiting, diarrhea, abdominal pain.
* **Dermatologic:** Rash, photosensitivity.
## Key Drug Interactions
* **Aminoglycosides, cisplatin, other ototoxic drugs:** Increased risk of ototoxicity.
* **ACE inhibitors, ARBs, other antihypertensives:** Additive hypotensive effects.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May decrease diuretic and antihypertensive effects and increase risk of renal impairment.
* **Lithium:** Increased risk of lithium toxicity due to decreased renal clearance.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* **Fluid and electrolytes:** Serum electrolytes (sodium, potassium, chloride, magnesium, calcium), BUN, creatinine, and urine output.
* **Blood pressure:** Monitor for hypotension.
* **Hearing:** Assess for signs of ototoxicity.
* **Glucose and uric acid:** Monitor for potential elevations.
## Clinical Pearls
* Furosemide is a potent diuretic; rapid diuresis can lead to significant fluid and electrolyte losses.
* Administer IV furosemide slowly (e.g., over 30-60 minutes) to minimize the risk of ototoxicity. Continuous infusion may be preferred for high-dose therapy.
* Oral and IV doses are not always 1:1. Generally, 20 mg IV is roughly equivalent to 40 mg orally, but this can vary.
* Hypokalemia is a common and significant adverse effect that can predispose patients to arrhythmias, especially those on digoxin. Potassium supplementation or potassium-sparing diuretics may be necessary.
* Monitor weight daily for patients on chronic therapy to assess fluid status.
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*Disclaimer: This information is intended for clinical use and does not replace professional medical judgment. Always consult the most current prescribing information and relevant literature before making clinical decisions.*
