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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver cirrhosis, and renal disease, including the nephrotic syndrome. It is also used to treat hypertension, alone or in combination with other antihypertensives.
## Primary Indications
* Edema (congestive heart failure, liver cirrhosis, renal disease, nephrotic syndrome)
* Hypertension
## Adult Dosing
* **Edema:**
* Oral: Start with 20-80 mg once daily. May increase by 20-40 mg every 6-8 hours as needed. Typical maintenance dose is 40-120 mg daily, but may require up to 600 mg daily in severe cases.
* IV/IM: Start with 20-40 mg once daily. May increase by 20 mg every 2 hours as needed. Higher doses may be required for severe edema.
* **Hypertension:**
* Oral: Start with 40 mg twice daily. Adjust dose based on response. Maximum dose is typically 80-120 mg daily, but higher doses may be used in refractory cases.
## Pediatric Dosing
* **Edema:**
* Oral: 1-4 mg/kg/day in 1-2 divided doses. Maximum: 40 mg/day.
* IV/IM: 1 mg/kg/dose. Maximum: 20 mg/dose. May repeat every 6-12 hours as needed. For severe edema or premature infants, doses up to 2 mg/kg/dose may be considered.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in renal impairment due to reduced renal clearance and protein binding. However, caution is advised as high doses can be nephrotoxic. Monitor response and electrolytes closely.
* **Hepatic Impairment:** Furosemide is generally well-tolerated, but fluid and electrolyte balance should be carefully monitored.
## Contraindications
* Anuria
* Known hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, dehydration, hyponatremia, hypokalemia, hypochloremia, hyperuricemia, hyperglycemia.
* **Less Common:** Hypotension, tinnitus, hearing loss (especially with rapid IV administration or high doses), rash, pruritus, photosensitivity, muscle cramps, pancreatitis, cholestatic jaundice, hepatic encephalopathy, blood dyscrasias (aplastic anemia, agranulocytosis, thrombocytopenia, leukopenia).
## Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May decrease furosemide's diuretic and antihypertensive effects. May also increase the risk of nephrotoxicity.
* **ACE inhibitors/ARBs:** Increased risk of hypotension and renal dysfunction, especially in volume-depleted patients.
* **Lithium:** Increased risk of lithium toxicity due to decreased renal excretion.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Antidiabetic agents:** May decrease their efficacy.
## Monitoring
* **Electrolytes:** Sodium, potassium, chloride, magnesium, calcium.
* **Renal function:** BUN, creatinine.
* **Fluid balance:** Intake and output, weight.
* **Blood pressure.**
* **Hearing** (especially with IV administration and high doses).
* **Blood glucose** in diabetic patients.
* **Uric acid levels.**
## Clinical Pearls
* Administer oral furosemide with food or milk to minimize gastric irritation.
* Rapid IV administration can cause ototoxicity; infuse slowly over 30-60 minutes (or longer for higher doses).
* For patients with severe edema unresponsive to oral therapy, continuous IV infusion may be more effective than intermittent boluses.
* Furosemide is highly protein-bound; in states of hypoalbuminemia, a higher dose may be required to achieve the same diuretic effect.
* Be aware of the potential for rebound edema when discontinuing furosemide.
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*This information is for educational purposes only and does not substitute professional medical advice. Always consult the current prescribing information and your healthcare provider for specific treatment decisions.*
