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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) associated with conditions such as heart failure, liver cirrhosis, and kidney disease, as well as hypertension.
## Primary Indications
* Edema due to congestive heart failure, liver cirrhosis, and renal disease (including the nephrotic syndrome).
* Hypertension (alone or in combination with other antihypertensives).
## Adult Dosing
* **Edema:**
* Oral: 20 mg to 80 mg once daily. If ineffective, dose may be increased by 20 mg to 40 mg every day or every other day. Maximum daily dose typically 600 mg, though higher doses may be used in specific inpatient settings under close monitoring. Doses may be divided for higher daily amounts.
* Intravenous (IV)/Intramuscular (IM): 20 mg to 40 mg once daily. If ineffective, dose may be increased by 20 mg to 40 mg. Maximum daily dose typically 600 mg, though higher doses may be used in specific inpatient settings under close monitoring. Doses may be divided for higher daily amounts.
* **Hypertension:**
* Oral: 40 mg twice daily. Doses may be adjusted based on response.
## Pediatric Dosing
* **Edema:**
* Oral: 1 mg/kg to 2 mg/kg once daily. If needed, increase by 1 mg/kg to 2 mg/kg every 6-8 hours. Maximum daily dose: 6 mg/kg.
* IV/IM: 1 mg/kg once daily. If needed, increase by 1 mg/kg every 2 hours. Maximum daily dose: 6 mg/kg.
* **Note:** Dosing in neonates and premature infants may require careful titration due to altered pharmacokinetics.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in renal impairment due to reduced renal clearance. However, prolonged or excessive doses can lead to ototoxicity.
* **Hepatic Impairment:** Dose may need to be decreased in hepatic impairment due to reduced metabolism and increased sensitivity.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
Common: Dizziness, lightheadedness, electrolyte imbalance (hypokalemia, hyponatremia, hypochloremia), dehydration, hypotension, ototoxicity (especially with rapid IV administration or high doses), hyperuricemia, hyperglycemia.
## Key Drug Interactions
* **Aminoglycosides/Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May decrease diuretic and antihypertensive effect.
* **Lithium:** May increase lithium levels, risk of toxicity.
* **Antihypertensives:** Additive hypotensive effect.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Renal function (BUN, creatinine).
* Blood pressure.
* Urine output.
* Auditory function (especially with high doses or prolonged therapy).
* Blood glucose in diabetic patients.
## Clinical Pearls
* Administer oral furosemide at least 6 hours before bedtime to minimize nocturia.
* Rapid IV administration (e.g., >4 mg/min or in boluses >20 mg) can increase the risk of ototoxicity. Consider continuous IV infusion for high doses.
* Monitor for signs and symptoms of electrolyte depletion (e.g., muscle cramps, weakness, confusion).
* IV and oral bioavailability can vary; do not assume equivalent dosing when switching formulations.
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**Disclaimer:** This information is intended for clinical use and does not replace the manufacturer's prescribing information or professional judgment. Always verify current prescribing information before dispensing or administering medication.
