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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) and high blood pressure. It works by inhibiting the Na-K-2Cl cotransporter 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, cirrhosis of the liver, and renal disease (including nephrotic syndrome).
* Hypertension, usually in combination with other antihypertensives.
## Adult Dosing
* **Edema:**
* Oral: 20-80 mg once daily. May increase by 20-40 mg every 6-8 hours as needed. Usual maintenance dose: 20-80 mg daily.
* Intravenous (IV) or Intramuscular (IM): 20-40 mg once daily. If insufficient response, may increase dose by 20 mg every 2 hours, or give 1-2 mg/kg in a single dose.
* Maximum oral dose: Not established, but doses > 600 mg daily have been used in severe cases.
* Maximum IV/IM dose: Not established, but commonly up to 200 mg/day. Higher doses may be required in specific situations, with careful monitoring.
* **Hypertension:**
* Oral: 40 mg twice daily. Not typically used as a first-line agent for hypertension unless edema is also present.
## Pediatric Dosing
Dosing is highly individualized and depends on the indication and patient response. **Consult specific pediatric guidelines or local protocols.**
* **Edema:**
* Oral: 1-2 mg/kg/dose once or twice daily. Maximum: 6 mg/kg/dose.
* IV/IM: 1 mg/kg/dose. Maximum: 20 mg/dose for premature infants, 40 mg/dose for term infants and children. May repeat every 6-12 hours.
* **Hypertension:** Generally not recommended for routine use in pediatrics.
## Dose Adjustments
* **Renal Impairment:** Patients with renal insufficiency may require lower initial doses and slower titration. May need higher doses to achieve diuresis.
* **Hepatic Impairment:** May require dose adjustments due to altered protein binding and metabolism.
## Contraindications
* Anuria.
* History of hypersensitivity to furosemide or sulfonamides (cross-sensitivity may occur).
## Adverse Effects
* **Electrolyte imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and hypotension.**
* **Ototoxicity:** Especially with rapid IV administration or high doses.
* **Hyperuricemia, hyperglycemia.**
* **Nephrotoxicity.**
* **Aplastic anemia, thrombocytopenia, leukopenia.**
* **Dizziness, lightheadedness.**
* **Photosensitivity.**
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **ACE inhibitors and ARBs:** Increased risk of hypotension and azotemia.
* **NSAIDs:** May reduce diuretic and antihypertensive effect; increased risk of nephrotoxicity.
* **Lithium:** Furosemide can decrease lithium clearance, increasing risk of lithium toxicity.
* **Potassium-sparing diuretics, potassium supplements:** Risk of hyperkalemia.
* **Corticosteroids:** May potentiate electrolyte depletion, particularly hypokalemia.
* **Digoxin:** Furosemide-induced hypokalemia increases digoxin cardiotoxicity risk.
## Monitoring
* **Electrolytes:** Serum electrolytes (sodium, potassium, chloride, magnesium, calcium) are crucial, especially with initiation or dose changes.
* **Renal function:** Serum creatinine and BUN.
* **Fluid status:** Daily weights, intake and output.
* **Blood pressure.**
* **Blood glucose** and **uric acid** (in susceptible patients).
## Clinical Pearls
* Furosemide is a high-ceiling diuretic; its effect increases with dose.
* Oral administration may be delayed by up to 1 hour compared to IV administration.
* IV administration should be slow (e.g., over 30-60 minutes) to minimize ototoxicity risk. Rapid IV bolus is generally avoided.
* Patients on furosemide require regular electrolyte monitoring and often potassium supplementation.
* For resistance to furosemide, consider increasing dose, changing to IV administration, or combining with another diuretic (e.g., thiazide).
***
**Disclaimer:** This information is for educational purposes only and does not substitute for professional medical advice. Always consult the most current prescribing information or a qualified healthcare provider for any drug-related questions or before making any treatment decisions.
