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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium and chloride in the ascending limb of the loop of Henle, leading to increased excretion of water, sodium, chloride, potassium, and hydrogen ions.
## Primary Indications
* Edema associated with congestive heart failure (CHF)
* Edema associated with liver cirrhosis
* Edema associated with renal disease, including the nephrotic syndrome
* Hypertension (IV use for acute, severe hypertension)
## Adult Dosing
* **Edema:**
* Oral: Start with 20-80 mg once daily. Doses may be given once or twice daily. If a once-daily dose is ineffective, the same total daily dose may be divided and given twice daily. Adjust dose based on response.
* IV/IM: Start with 20-40 mg once daily. If needed, doses can be repeated every 2 hours.
* Maximum effective dose is generally considered 80 mg in a single dose for patients not previously receiving diuretics. Higher doses may be effective but increase the risk of adverse effects.
* **Hypertension (Adjunctive therapy):**
* Oral: 40 mg twice daily.
* **Acute Pulmonary Edema:**
* IV: 40 mg. If inadequate response within 1 hour, administer an additional 80 mg IV.
## Pediatric Dosing
* **Edema:**
* Oral: 1-4 mg/kg/dose once daily. Maximum dose: 40 mg/day.
* IV/IM: 1 mg/kg/dose once daily. Maximum dose: 20 mg/dose.
* Continuous infusion (IV): 0.1-1 mg/kg/hour.
## Dose Adjustments
* **Renal Impairment:** Dose reduction is often necessary, but the optimal dose is highly individualized. Monitor for response and adverse effects. Patients with significant renal impairment may require higher doses or continuous infusions.
* **Hepatic Impairment:** Furosemide may accumulate. Monitor electrolytes and fluid status closely.
## Contraindications
* Anuria
* History of hypersensitivity to furosemide or sulfonamides
## Adverse Effects
* Electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia)
* Dehydration
* Hypotension
* Ototoxicity (especially with rapid IV administration or high doses)
* Hyperuricemia
* Hyperglycemia
* Photosensitivity
* Aplastic anemia, agranulocytosis, thrombocytopenia
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **ACE inhibitors and ARBs:** Increased risk of hypotension and renal dysfunction.
* **NSAIDs:** May reduce diuretic and antihypertensive effect.
* **Digoxin:** Risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Lithium:** Furosemide can decrease lithium clearance, increasing the risk of lithium toxicity.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Fluid status (weight, urine output, edema)
* Blood pressure
* Hearing (especially with high doses or IV administration)
* Blood glucose (in diabetic patients)
* Uric acid (in patients with gout)
## Clinical Pearls
* Oral furosemide can be administered once or twice daily. If given twice daily, separate doses by 6-8 hours.
* IV administration leads to a more rapid onset of action.
* Rapid IV administration (e.g., faster than 4 mg/minute) can lead to ototoxicity. Administer IV furosemide slowly.
* Patients may develop tolerance to the diuretic effects with chronic use.
* Consider potassium supplementation or potassium-sparing diuretics in patients at risk for hypokalemia.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant guidelines before making clinical decisions.*
