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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, potassium, chloride, calcium, and magnesium.
## Primary Indications
* Edema associated with congestive heart failure
* Hepatic cirrhosis
* Renal disease (including the nephrotic syndrome)
* Hypertension (adjunctive therapy)
## Adult Dosing
* **Edema:**
* Oral: 20-80 mg once daily, may increase by 20-40 mg every 6-8 hours as needed. Usual maintenance dose is 40-80 mg daily. Maximum recommended oral dose is 600 mg/day (higher doses may be used in severe edema under close medical supervision).
* IV/IM: 20-40 mg once daily, may increase by 20 mg every 2 hours as needed. Usual maintenance dose is 40-80 mg daily. Maximum recommended IV dose is 600 mg/day (higher doses may be used in severe edema under close medical supervision).
* **Hypertension:**
* Oral: 40 mg twice daily.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose once daily. If inadequate response, doses may be increased by 1-2 mg/kg/dose every 6-8 hours. Maximum dose 6 mg/kg/dose.
* IV/IM: 1 mg/kg/dose. If inadequate response, doses may be increased by 1 mg/kg/dose every 2 hours. Maximum dose 6 mg/kg/dose.
* *Note:* In premature infants, lower doses may be required. Dosing in neonates is highly variable and requires careful monitoring.
## Dose Adjustments
* **Renal Impairment:** In patients with significant renal impairment, doses may need to be increased, but the response may be less predictable. Continuous IV infusion may be more effective.
* **Hepatic Impairment:** Caution is advised; electrolyte and fluid balance must be carefully monitored.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides (cross-sensitivity possible)
* Severe electrolyte depletion (e.g., hypokalemia, hyponatremia)
## Adverse Effects
* **Common:** Dizziness, lightheadedness, orthostatic hypotension, hearing impairment (especially with rapid IV administration or high doses), hyponatremia, hypochloremia, hypokalemia, hyperglycemia.
* **Less Common/Serious:** Dehydration, azotemia, renal failure, pancreatitis, cholestatic jaundice, aplastic anemia, thrombocytopenia, agranulocytosis, rash, photosensitivity, Stevens-Johnson syndrome.
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **Antihypertensives (including other diuretics):** Potentiated hypotensive effect.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May reduce the diuretic and natriuretic effect.
* **Lithium:** Increased risk of lithium toxicity.
* **Neuromuscular blocking agents:** May potentiate the effects.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Blood pressure (especially with upright posture)
* Urine output
* Hearing (assess for tinnitus or hearing loss)
* Blood glucose (in diabetic patients)
## Clinical Pearls
* Furosemide is a potent diuretic; initiation and titration should be done cautiously.
* Rapid IV administration can cause ototoxicity and hypotension. Administer IV doses slowly, typically over 30-60 minutes.
* Oral administration is generally preferred for chronic management.
* Electrolyte imbalances, particularly hypokalemia, are common and can lead to serious cardiac arrhythmias or potentiate digoxin toxicity.
* Patients taking furosemide should be advised to rise slowly from sitting or lying positions to minimize orthostatic hypotension.
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**Disclaimer:** This information is intended for clinical use and does not replace professional medical advice. Always consult the most current prescribing information and relevant guidelines for complete details and to verify dosage and safety information before administering any medication.
