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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, cirrhosis, and renal disease, including nephrotic syndrome. It is also used to manage hypertension, although it's typically not a first-line agent for this indication alone.
## Primary Indications
* Edema (congestive heart failure, hepatic cirrhosis, renal disease)
* Hypertension (adjunct therapy)
## Adult Dosing
* **Edema:**
* Oral: Initial dose is typically 20-80 mg once daily. The dose may be increased by 20-40 mg every 6-8 hours as needed until desired response is achieved. Doses can be given once or twice daily.
* IV/IM: Initial dose is typically 20-40 mg once daily. If ineffective, subsequent doses can be increased by 20 mg every 2 hours.
* Maximum daily oral dose: Generally 600 mg, but higher doses have been used under close medical supervision.
* Maximum daily IV/IM dose: Generally 100 mg, but higher doses have been used under close medical supervision.
* **Hypertension:**
* Oral: 40 mg twice daily. This is usually used in patients with significant edema or impaired renal function.
* **Continuous IV Infusion for Edema:**
* An initial IV bolus of 80 mg followed by a continuous infusion of 10 mg/hour has been used.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose once or twice daily. Maximum 6 mg/kg/day.
* IV/IM: 1 mg/kg/dose once or twice daily. Maximum 6 mg/kg/day.
* **Hypertension:** Dosing in pediatric hypertension is not well-established and should be guided by specialist recommendations.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with renal insufficiency due to impaired drug excretion. However, patients with severe renal failure may be refractory to furosemide.
* **Hepatic Impairment:** Dose reductions may be necessary in patients with cirrhosis and ascites due to increased bioavailability and potential for accumulation.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides
## Adverse Effects
* **Common:** Dizziness, lightheadedness, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), dehydration, hypotension, hyperglycemia.
* **Serious:** Severe electrolyte depletion, ototoxicity (especially with rapid IV administration or in renal impairment), Stevens-Johnson syndrome, aplastic anemia, acute kidney injury.
## Key Drug Interactions
* **Aminoglycosides/Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May reduce the diuretic and antihypertensive effects of furosemide.
* **Antihypertensives:** Additive hypotensive effects.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Lithium:** Increased risk of lithium toxicity.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Blood pressure
* Urine output
* Fluid balance (weight)
* Blood glucose (in diabetic patients)
* Hearing (especially with high doses or prolonged therapy)
## Clinical Pearls
* Administer IV furosemide slowly (no faster than 4 mg/min) to reduce the risk of ototoxicity. Rapid IV injection has been associated with temporary or permanent hearing impairment.
* Oral administration should ideally occur in the morning to minimize nocturia.
* Patients taking furosemide should have their electrolytes monitored regularly, especially those on concurrent medications that can affect electrolyte levels or those with risk factors for electrolyte disturbances.
* Weight monitoring is a crucial indicator of fluid status in patients with edema.
* The bioavailability of oral furosemide can be variable, particularly in patients with severe edema or gastrointestinal disease.
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*This information is intended for healthcare professionals. Always verify the most current prescribing information and local protocols before administering medication.*
