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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) due to heart failure, liver disease, or kidney disease. It can also be used to treat high blood pressure.
## Primary Indications
* Edema associated with congestive heart failure (CHF), cirrhosis, and renal disease.
* Hypertension.
## Adult Dosing
* **Edema:**
* **Oral:** Initial dose 20-80 mg once daily. May increase by 20-40 mg every 6-8 hours as needed. Usual maintenance dose 20-80 mg daily, may be given in divided doses.
* **Intravenous (IV) or Intramuscular (IM):** Initial dose 20-40 mg once daily. May increase by 20 mg every 2 hours as needed. Usual maintenance dose 40-80 mg daily, may be given in divided doses.
* **Maximum Oral/IV/IM dose:** Generally not to exceed 600 mg/day for chronic use, though higher doses have been used in specific situations under close supervision.
* **Hypertension:**
* **Oral:** 40 mg twice daily. This use is generally limited to patients with concurrent edema.
## Pediatric Dosing
* **Edema:**
* **Oral:** 1-2 mg/kg/dose once daily. Doses may be increased by 1 mg/kg/dose every 6-8 hours to achieve desired response. Maximum dose: 6 mg/kg/day.
* **IV:** 1 mg/kg/dose once daily. Doses may be increased by 0.5-1 mg/kg/dose every 2 hours as needed. Maximum dose: 6 mg/kg/day.
* **Continuous IV Infusion:** 0.1 mg/kg/hour.
## Dose Adjustments
* **Renal Impairment:** Doses may need to be increased in renal impairment due to reduced efficacy and increased half-life. Close monitoring of fluid status and electrolytes is essential.
* **Hepatic Impairment:** Use with caution due to potential for rapid fluid and electrolyte losses, which can precipitate hepatic encephalopathy.
## Contraindications
* Anuria.
* History of hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Electrolyte imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration:** Dizziness, lightheadedness, hypotension.
* **Ototoxicity:** Tinnitus, hearing loss (especially with rapid IV administration or in patients with renal impairment).
* **Hyperglycemia:** May worsen glycemic control in diabetic patients.
* **Hyperuricemia:** May precipitate gout.
* **Photosensitivity.**
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Antihypertensives (including ACE inhibitors, ARBs, beta-blockers):** Additive hypotensive effect.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May reduce furosemide's diuretic and antihypertensive effects.
* **Potassium-sparing diuretics:** May be used to counteract potassium loss, but monitor electrolytes closely.
* **Thiazide diuretics:** Additive diuretic effect.
## Monitoring
* **Electrolytes:** Serum electrolytes (sodium, potassium, chloride, magnesium, calcium) are crucial, especially with initiation or dose changes, and in patients with risk factors.
* **Fluid Status:** Monitor daily weights, intake and output, and signs of edema and dehydration.
* **Renal Function:** Serum creatinine and BUN.
* **Blood Pressure:** Especially in hypertensive patients.
* **Blood Glucose:** In diabetic patients.
* **Hearing:** Assess for tinnitus or hearing impairment.
## Clinical Pearls
* Administer oral furosemide in the morning to minimize nocturia.
* Rapid IV administration can increase the risk of ototoxicity. Administer IV infusion slowly, typically over 30-60 minutes.
* In patients with severe edema, a continuous IV infusion may be more effective than intermittent bolus doses.
* Potassium supplementation or coadministration of a potassium-sparing diuretic may be necessary to prevent or treat hypokalemia.
* Patients with significant edema may require higher doses due to altered pharmacokinetics.
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*Disclaimer: This information is for educational purposes only and does not substitute for professional medical advice. Always consult with a qualified healthcare provider to ensure the information provided is appropriate for your specific situation and to review the most current prescribing information.*
