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# Furosemide (Lasix)
## 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 typically not as a first-line agent.
## Primary Indications
* Edema due to congestive heart failure (CHF)
* Edema due to liver cirrhosis
* Edema due to renal disease, including the nephrotic syndrome
* Hypertension (adjunctive therapy)
## Adult Dosing
* **Edema:**
* **Starting Dose:** 20 mg to 80 mg orally once daily.
* **Higher Doses:** May be given as a single dose or divided doses. Doses up to 600 mg orally daily have been used in refractory cases, but typically lower doses are sufficient. The dose should be titrated to the smallest effective dose.
* **Intravenous (IV) or Intramuscular (IM):** 20 mg to 40 mg once daily. For more rapid or potent diuresis, doses up to 80 mg IV or IM once daily can be given. Higher doses may be needed for severe edema. Conversion from oral to IV/IM may require a 1:1 ratio initially, but some sources suggest IV may be more potent.
* **Hypertension:**
* **Starting Dose:** 40 mg orally once daily.
* **Maintenance Dose:** 20 mg to 40 mg orally once daily.
* **Maximum:** Doses above 40 mg orally daily are generally not recommended for hypertension due to diminishing antihypertensive effect and increased diuretic effect.
## Pediatric Dosing
* **Edema:**
* **Oral:** 1 mg/kg to 2 mg/kg per dose once daily, not to exceed 6 mg/kg/day. Doses may be given once or twice daily.
* **IV/IM:** 1 mg/kg per dose once daily, not to exceed 6 mg/kg/day. Higher doses may be required in premature infants.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with renal impairment due to decreased renal excretion and binding of furosemide. However, careful monitoring is essential as accumulation can occur. Dosing in severe renal failure can be complex and requires careful titration.
* **Hepatic Impairment:** Use with caution; dose adjustment may be necessary.
## Contraindications
* Anuria
* Known hypersensitivity to furosemide or sulfonamides (potential for cross-sensitivity).
## Adverse Effects
* **Common:** Dizziness, lightheadedness, electrolyte imbalance (hypokalemia, hyponatremia, hypochloremia), dehydration, hypotension, hyperuricemia.
* **Serious:** Severe electrolyte depletion, ototoxicity (especially with rapid IV administration or in renal impairment), hyperglycemia, pancreatitis, cholestatic jaundice, aplastic anemia, agranulocytosis, Stevens-Johnson syndrome.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Antihypertensives (including ACE inhibitors, ARBs, beta-blockers):** Additive hypotensive effects.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May diminish the diuretic and antihypertensive effects of furosemide and increase the risk of nephrotoxicity.
* **Potassium supplements or potassium-sparing diuretics:** Monitor electrolytes closely due to potential for additive effects or counteraction.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Fluid balance (intake and output, weight changes)
* Blood pressure
* Blood glucose (in diabetic patients)
* Hearing (especially with high doses or rapid IV infusion)
## Clinical Pearls
* Furosemide is a potent diuretic; onset of action is rapid (oral: 30-60 minutes; IV: within 5 minutes).
* Administer IV furosemide slowly (e.g., over 30-60 minutes) to minimize the risk of ototoxicity. Rapid IV push can cause sudden hearing loss.
* For patients with severe edema, a continuous IV infusion may be more effective than intermittent boluses.
* Electrolyte monitoring is crucial, particularly for potassium, to prevent arrhythmias and other complications.
* Patients with heart failure may require higher doses to achieve desired diuresis due to altered pharmacokinetics.
* Consider switching to an oral formulation once the patient is stabilized.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for clinical judgment. Always refer to the official prescribing information and institutional protocols for complete details and to verify current recommendations.
