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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the Na-K-2Cl symporter in the thick ascending limb of the loop of Henle, leading to increased excretion of sodium, chloride, potassium, and water.
## Primary Indications
* Edema associated with congestive heart failure (CHF)
* Hepatic cirrhosis
* Renal disease, including nephrotic syndrome
* Pulmonary edema (acute)
* Hypertension (adjunct therapy)
## Adult Dosing
* **Edema:**
* Initial: 20-80 mg PO once daily. May be given as a single dose or divided.
* Subsequent: Doses may be increased by 20-40 mg every 6-8 hours as needed.
* Maximum: 600 mg/day (higher doses may be used in severe edema under close medical supervision, but efficacy and safety are not well established).
* **Hypertension:**
* Initial: 40 mg PO twice daily.
* Maintenance: Adjust dose as needed.
* **Acute Pulmonary Edema:**
* Initial: 40 mg IV.
* Subsequent: 20-40 mg IV may be administered 1-2 hours after the initial dose if indicated.
* **Note:** Intravenous doses are generally twice the oral dose.
## Pediatric Dosing
* **Edema/Hypertension:**
* 0.5-2 mg/kg/dose PO or IV every 6-12 hours.
* Maximum: 6 mg/kg/day.
* **Neonates:** Use with caution due to potential for prolonged effect. Dosing may vary; consult specialized resources.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased due to impaired excretion. Close monitoring of fluid status and electrolytes is essential. In patients with significant renal impairment, doses up to 4 g/day have been used, but this requires careful titration and monitoring.
* **Hepatic Impairment:** Dose adjustments may be necessary; however, furosemide is often less effective in severe hepatic disease.
## Contraindications
* Anuria
* Known hypersensitivity to furosemide or sulfonamides
## Adverse Effects
* **Common:** Dizziness, lightheadedness, orthostatic hypotension, dehydration, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), azotemia, hyperglycemia.
* **Less Common:** Ototoxicity (especially with rapid IV administration or high doses), rash, pruritus, photosensitivity, gastrointestinal upset, pancreatitis, aplastic anemia, agranulocytosis.
## Key Drug Interactions
* **Aminoglycosides/Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effects.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Antihypertensives:** Additive hypotensive effects.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, increasing risk of lithium toxicity.
* **Diabetic Medications:** May decrease efficacy.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Fluid balance (intake/output, daily weights)
* Blood pressure
* Hearing (especially with high doses or rapid IV administration)
* Blood glucose levels in diabetic patients
## Clinical Pearls
* Furosemide is a potent diuretic; initiation and dose adjustments should be gradual.
* Oral administration is preferred when possible.
* Administer IV furosemide slowly to minimize the risk of ototoxicity.
* Monitor for signs and symptoms of electrolyte depletion, especially hypokalemia. Potassium supplementation may be necessary.
* Advise patients to rise slowly from a sitting or lying position to minimize orthostatic hypotension.
* Educate patients on the importance of consistent fluid intake and monitoring daily weights.
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**Disclaimer:** This information is intended for clinical pharmacists and is not a substitute for complete prescribing information. Always verify current prescribing information and consult relevant guidelines before making clinical decisions.
