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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to reduce fluid overload.
## Primary Indications
* Edema associated with congestive heart failure (CHF), liver disease (cirrhosis), and renal disease, including the nephrotic syndrome.
* Hypertension (less commonly as monotherapy).
## Adult Dosing
* **Edema:** Oral: Initiate at 20-80 mg once daily. May increase by 20-40 mg every 6-8 hours as needed. Maximum dose: 600 mg/day (higher doses may be used in hospitalized patients under close supervision).
* IV/IM: Initiate at 20-40 mg once daily. May increase by 20 mg every 2 hours as needed. Maximum dose: 600 mg/day (higher doses may be used in hospitalized patients under close supervision).
* **Hypertension:** Oral: 40 mg twice daily.
* **Acute Pulmonary Edema:** IV: 40 mg administered slowly. If no adequate response, a second dose of 80 mg IV may be given.
*Note: Dosing for edema is highly individualized and dependent on the severity of fluid overload and patient response. Doses may need to be titrated aggressively in some cases, especially for severe edema or when switching from IV to oral.*
## Pediatric Dosing
* **Edema:** Oral: 1-4 mg/kg/day in divided doses (typically twice daily). Maximum dose: 40 mg/day.
* IV/IM: 1 mg/kg/dose. May increase by 1 mg/kg/dose every 2 hours as needed. Maximum dose: 40 mg/day.
* Continuous IV infusion: 0.1 mg/kg/hour.
*Note: Dosing in neonates and infants can be variable; close monitoring is essential.*
## Dose Adjustments
* **Renal Impairment:** Furosemide is largely eliminated by the kidneys. Dose may need to be increased in renal impairment due to decreased efficacy, or decreased if accumulation occurs. Continuous infusion may be more effective than bolus dosing in some patients with severe renal dysfunction.
* **Hepatic Impairment:** Caution and close monitoring due to potential for electrolyte imbalances and hepatic encephalopathy.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), dehydration, hypotension, polyuria, hyperuricemia.
* **Serious:** Severe electrolyte disturbances, ototoxicity (especially with rapid IV administration or high doses), rash (including Stevens-Johnson syndrome), aplastic anemia, pancreatitis, cholestatic jaundice.
## Key Drug Interactions
* **Aminoglycosides, other ototoxic drugs:** Increased risk of ototoxicity.
* **ACE inhibitors, ARBs, other antihypertensives:** Additive hypotensive effect.
* **NSAIDs:** May reduce diuretic and antihypertensive effects; increase risk of renal impairment.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, increasing lithium toxicity risk.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Renal function (BUN, creatinine).
* Blood pressure.
* Fluid balance (intake/output, daily weights).
* Hearing (especially with high doses or risk factors for ototoxicity).
* Blood glucose in diabetic patients.
* Uric acid levels.
## Clinical Pearls
* Furosemide's effectiveness can be blunted by NSAIDs.
* Rapid IV administration can increase the risk of ototoxicity. Administer IV furosemide over at least 30-60 minutes, or as a continuous infusion in critically ill patients.
* Hypokalemia is a significant concern; consider potassium supplementation or a potassium-sparing diuretic if indicated.
* Monitor for signs of dehydration and hypotension.
* In patients with severe edema unresponsive to oral therapy, IV administration or continuous infusion may be necessary.
**Disclaimer:** Always consult the most current prescribing information and institutional protocols for definitive guidance. This information is intended for healthcare professionals and does not substitute professional judgment.
