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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) due to conditions such as heart failure, liver disease, and kidney disease. It is also used to treat high blood pressure, usually in combination with other antihypertensives.
## Primary Indications
* Edema associated with congestive heart failure, cirrhosis, and renal disease.
* Hypertension (adjunctive therapy).
## Adult Dosing
* **Edema:**
* Oral: 20 mg to 80 mg once daily. Doses may be increased by 20 mg to 40 mg every 6 to 8 hours as needed. Doses greater than 80 mg should generally be administered by intermittent intravenous infusion.
* Intravenous (IV) or Intramuscular (IM): 20 mg to 40 mg once daily. Doses may be increased by 20 mg to 40 mg every 2 hours as needed.
* Continuous IV infusion: Initiate at a rate of 4 mg/hour. Adjust dose based on response.
* Maximum oral dose: Typically 600 mg daily, but higher doses may be used in specific refractory cases under close monitoring.
* Maximum IV/IM dose: Typically 200 mg in a single dose, but higher doses may be used in specific refractory cases under close monitoring.
* **Hypertension:**
* Oral: 40 mg twice daily. Doses are usually adjusted based on response. Furosemide is generally not recommended as a sole agent for hypertension.
## Pediatric Dosing
* **Edema:**
* Oral: 1 mg/kg/dose to 2 mg/kg/dose every 6 to 12 hours.
* IV/IM: 1 mg/kg/dose to 2 mg/kg/dose every 6 to 12 hours.
* Continuous IV infusion: 0.1 mg/kg/hour.
* Maximum daily dose for oral or IV/IM: 6 mg/kg.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased due to impaired excretion. However, monitor for ototoxicity with high doses.
* **Hepatic Impairment:** Monitor for electrolyte imbalances and hepatic encephalopathy. Dosing adjustments are not routinely specified, but close monitoring is essential.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, dehydration, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), hyperuricemia, hyperglycemia.
* **Serious:** Hypotension, ototoxicity (hearing loss, tinnitus, often reversible), severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis), pancreatitis, blood dyscrasias, acute kidney injury.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **NSAIDs:** May decrease diuretic and antihypertensive effects and increase risk of renal impairment.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** May reduce lithium clearance, increasing the risk of lithium toxicity.
* **Antihypertensives:** Additive hypotensive effects.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Blood pressure
* Urine output
* Blood glucose (in diabetics)
* Uric acid
* Auditory function (especially with high doses or in susceptible patients)
## Clinical Pearls
* Administer oral furosemide in the morning to minimize nocturnal diuresis.
* When switching from IV to oral therapy, the oral dose should generally be 1:1 or 2:1 compared to the IV dose, depending on local protocols and clinical response.
* Electrolyte replacement, particularly potassium, may be necessary, especially with prolonged use or high doses.
* Monitor for signs of dehydration and hypotension.
* Ototoxicity is more likely with rapid IV administration of high doses.
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*This information is intended for healthcare professionals. Please consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions.*
