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## Furosemide (Lasix)
### Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver disease, and renal disease, including the nephrotic syndrome. It is also used to treat hypertension, alone or in combination with other antihypertensives.
### Primary Indications
* Edema (heart failure, cirrhosis, renal disease, nephrotic syndrome)
* Hypertension
### Adult Dosing
* **Edema:** Initial dose is typically 20-80 mg orally once daily. Doses may be increased by 20-40 mg every 6-8 hours as needed. The usual maintenance dose is 40 mg orally once daily. Doses can be titrated up to 600 mg/day in severe cases, but doses above 80 mg are usually given in divided doses. Intravenous or intramuscular dosing is generally 2.5 times the oral dose.
* **Hypertension:** Initial dose is 40 mg orally once daily. Maintenance dose is 40 mg orally once daily. For resistant hypertension, higher doses may be used, often in combination with other agents.
### Pediatric Dosing
* **Edema:** 1-4 mg/kg/day orally in divided doses every 6-12 hours. Doses should not exceed 40 mg per dose, unless on specialized care. Intravenous or intramuscular dosing is 1 mg/kg/dose, not to exceed 20 mg per dose.
* **Neonates:** Initial dose is 0.5-1 mg/kg/dose intravenously or intramuscularly every 12-24 hours. Doses may be increased to 2 mg/kg/dose every 8-12 hours. For chronic therapy, a dose of 0.5-1 mg/kg/day may be used.
### Dose Adjustments
* **Renal Impairment:** Furosemide is renally eliminated. In severe renal impairment, the dose may need to be increased, and/or the dosing interval extended. Patients with renal failure may require very high doses.
* **Hepatic Impairment:** In patients with cirrhosis, ascites, and electrolyte disturbances, cautious dosing is recommended due to increased risk of ototoxicity and electrolyte imbalances.
### Contraindications
* Anuria
* Known hypersensitivity to furosemide or sulfonamides (cross-sensitivity may occur).
### Adverse Effects
Common adverse effects include dizziness, lightheadedness, orthostatic hypotension, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), hyperuricemia, hyperglycemia, dehydration, and azotemia. Less common but serious effects include ototoxicity (especially with rapid IV administration or high doses), Stevens-Johnson syndrome, and aplastic anemia.
### Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **ACE inhibitors/ARBs:** Increased risk of hypotension and renal dysfunction.
* **NSAIDs:** May reduce diuretic and antihypertensive effect and increase risk of renal impairment.
* **Digoxin:** Hypokalemia induced by furosemide can increase digoxin toxicity.
* **Lithium:** Furosemide can decrease renal clearance of lithium, increasing lithium toxicity risk.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Antidiabetic agents:** May decrease effectiveness.
### Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Blood pressure
* Fluid status (weight, edema)
* Blood glucose (in diabetics)
* Uric acid
* Hearing (especially with high doses or risk factors)
### Clinical Pearls
* Furosemide is a potent diuretic; administer once daily in the morning for edema to minimize nocturia.
* Rapid intravenous administration can lead to ototoxicity. Administer IV furosemide slowly (e.g., over 1-2 minutes) or as a continuous infusion.
* Monitor electrolytes closely, especially potassium. Consider potassium supplementation or a potassium-sparing diuretic if hypokalemia is significant.
* For resistant edema, consider concomitant administration of a thiazide diuretic.
* Ensure adequate hydration to prevent excessive volume depletion and electrolyte abnormalities.
**Disclaimer:** This information is intended for clinical use and does not replace comprehensive drug references or local institutional protocols. Always verify current prescribing information for the most up-to-date and complete details.
