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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), cirrhosis, and renal disease (including nephrotic syndrome).
* Hypertension (alone or in combination with other antihypertensives).
## Adult Dosing
* **Edema:** Oral: 20-80 mg once daily. Doses may be given every day, every other day, or every few days depending on response. The usual dose is 40 mg/day. Doses up to 600 mg/day have been used in severe cases, but typically require careful monitoring.
* **Edema (IV/IM):** 20-40 mg once daily. Further doses of 20 mg or increments of 20 mg may be administered every 2-4 hours until desired response is achieved. In patients refractory to oral therapy, higher doses may be needed (e.g., 80-120 mg IV). Continuous IV infusion may be considered for severe edema.
* **Hypertension:** Oral: 40 mg twice daily. Not recommended as first-line therapy for hypertension.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose once daily. Do not exceed 6 mg/kg/day.
* IV/IM: 1 mg/kg/dose once daily. Do not exceed 20 mg/dose. Higher doses (e.g., 1-2 mg/kg/dose) may be given every 6-12 hours for severe cases.
* **Neonates:** May have altered pharmacokinetics. Doses of 0.5-1 mg/kg/dose IV/IM every 12-24 hours.
## Dose Adjustments
* **Renal Impairment:** Dose adjustment is often necessary. Monitor for efficacy and toxicity. Higher doses may be required due to resistance.
* **Hepatic Impairment:** Monitor closely for electrolyte imbalances and hepatic encephalopathy. Dose may need to be reduced.
## Contraindications
* Anuria.
* Hypersensitivity to furosemide or sulfonamides.
* History of severe allergic reaction to sulfonamides may indicate a contraindication.
## Adverse Effects
* **Common:** Electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), dehydration, hypotension, dizziness, headache, hyperuricemia (may precipitate gout), hyperglycemia.
* **Less Common:** Ototoxicity (especially with rapid IV administration or high doses), rash, photosensitivity, pancreatitis, Aplastic anemia, Thrombocytopenia, Agranulocytosis.
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **ACE inhibitors and ARBs:** Increased risk of hypotension and acute kidney injury.
* **NSAIDs:** May decrease diuretic and antihypertensive effect, and increase risk of kidney damage.
* **Potassium-sparing diuretics, ACE inhibitors, ARBs, spironolactone, triamterene, amiloride:** Increased risk of hyperkalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Increased risk of lithium toxicity due to furosemide-induced sodium depletion.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Fluid balance (intake/output, daily weights)
* Blood pressure
* Blood glucose (in diabetic patients)
* Uric acid
## Clinical Pearls
* Administer oral furosemide in the morning to minimize nocturia.
* Rapid IV administration (e.g., > 4 mg/min) can lead to ototoxicity. Infuse IV doses slowly, typically over 1-2 minutes, or use continuous infusion for higher doses.
* Monitor for signs and symptoms of dehydration and electrolyte abnormalities, especially hypokalemia. Potassium supplementation or use of potassium-sparing diuretics may be necessary.
* Furosemide's potency and duration of action can vary significantly between patients. Dosing may need frequent adjustment.
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**Disclaimer:** This information is intended for educational purposes and does not substitute for professional medical advice. Always consult current prescribing information and your healthcare provider for specific patient care decisions.
