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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium and chloride in the thick ascending limb of the loop of Henle, leading to increased excretion of water, sodium, chloride, potassium, calcium, and magnesium.
## Primary Indications
* Edema associated with congestive heart failure (CHF)
* Edema associated with hepatic cirrhosis
* Edema associated with renal disease, including nephrotic syndrome
* Hypertension (adjunctive therapy, usually when edema is present)
## Adult Dosing
* **Edema:**
* Oral: Starting dose 20-80 mg once daily. May increase by 20-40 mg every 6-8 hours as needed. Usual dose range 20-80 mg/day, but doses up to 600 mg/day have been used in severe cases.
* Intravenous (IV) or Intramuscular (IM): Starting dose 20-40 mg once daily. May increase by 20 mg every 2 hours as needed. Usual dose range 20-40 mg/day. In patients resistant to oral therapy, higher doses may be required. Continuous IV infusion: 4 mg/hour after an initial bolus dose of 40 mg.
* **Hypertension:**
* Oral: 40 mg twice daily. Doses may vary.
* **Acute Pulmonary Edema:**
* IV: 20-40 mg. If patient does not respond, may give an additional 20 mg after 2 hours.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose once daily. If insufficient response, may increase dose by 1-2 mg/kg/dose every 6-8 hours. Maximum dose: 6 mg/kg/day.
* IV or IM: 1 mg/kg/dose once daily. If insufficient response, may increase dose by 1 mg/kg/dose every 2 hours. Maximum dose: 6 mg/kg/day. For premature infants, doses may be lower and administered less frequently.
## Dose Adjustments
* **Renal Impairment:** Patients with renal insufficiency may require higher doses due to impaired drug excretion. Close monitoring is essential.
* **Hepatic Impairment:** Can lead to increased sensitivity. Monitor electrolytes and fluid status closely.
## Contraindications
* Anuria
* History of hypersensitivity to furosemide or sulfonamides (cross-sensitivity may occur)
* Hepatic coma or severe electrolyte depletion
## Adverse Effects
* **Common:** Dizziness, lightheadedness, blurred vision, headache, hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia, dehydration, hyperuricemia (may precipitate gout), hyperglycemia, orthostatic hypotension.
* **Less Common/Rare:** Ototoxicity (especially with rapid IV administration or high doses), pancreatitis, cholestatic jaundice, hepatitis, aplastic anemia, thrombocytopenia, agranulocytosis, Stevens-Johnson syndrome, exfoliative dermatitis.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Corticosteroids (systemic):** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Decreased lithium clearance, increasing risk of lithium toxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effects.
* **Other Antihypertensives:** Additive hypotensive effects.
* **Sucralfate:** May decrease absorption of furosemide; administer furosemide at least 2 hours before or after sucralfate.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Blood glucose
* Uric acid
* Fluid balance (intake and output)
* Blood pressure
* Hearing (especially with high doses or IV administration)
## Clinical Pearls
* Administer oral furosemide on an empty stomach for maximum absorption; however, if GI upset occurs, it can be taken with food or milk.
* Timing of administration can be important to minimize nocturia (e.g., avoid doses late in the evening).
* Rapid IV injection can cause ototoxicity. Administer IV doses slowly over 30-60 minutes or as a continuous infusion.
* Be aware of the potential for electrolyte imbalances, especially hypokalemia, which can increase the risk of cardiac arrhythmias.
* Patients with sulfonamide allergies should be monitored closely for hypersensitivity reactions.
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*This information is intended for healthcare professionals. Please consult the most current prescribing information and relevant clinical guidelines for complete details and to verify accuracy before making therapeutic decisions.*
