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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to reduce edema and manage hypertension. It inhibits sodium and chloride reabsorption in the ascending limb of the loop of Henle, leading to increased excretion of water, sodium, potassium, chloride, calcium, and magnesium.
## Primary Indications
* Edema associated with congestive heart failure (CHF)
* Edema associated with hepatic cirrhosis
* Edema associated with renal disease, including nephrotic syndrome
* Hypertension (parenteral use only, typically in acute settings)
* Acute pulmonary edema
## Adult Dosing
* **Edema:** Oral: 20-80 mg once daily. If needed, doses may be increased by 20-40 mg every 6-8 hours. Maximum oral dose is typically 600 mg/day, but higher doses may be used in specific, monitored settings.
* **Edema:** Intravenous (IV) or Intramuscular (IM): 20-40 mg once daily. If inadequate response, dose can be increased by 20 mg every 2 hours or by 40 mg every 4 hours. Maximum IV/IM dose is typically 200 mg per dose, but higher doses may be used in specific, monitored settings.
* **Acute Pulmonary Edema:** IV: 40 mg. If inadequate response after 2 hours, 80 mg IV. May increase dose by 40-80 mg every 2 hours.
* **Hypertension:** Parenteral use is generally reserved for patients who cannot take oral medication or require rapid diuresis. IV/IM: 20-40 mg. May be repeated every 6-8 hours. Generally not a first-line agent for chronic hypertension.
## Pediatric Dosing
Dosing varies based on age, weight, and indication. Dosing should be determined based on local protocol and clinical judgment.
* **Edema/Hypertension (Oral):** 1-2 mg/kg/dose every 6-12 hours. Maximum dose: 6 mg/kg/day.
* **Edema/Hypertension (IV/IM):** 1 mg/kg/dose every 6-12 hours. Maximum dose: 6 mg/kg/day.
* **Neonates (IV/IM):** 0.5-1 mg/kg/dose every 12-24 hours.
* **Premature Infants (IV/IM):** 0.5-1 mg/kg/dose every 24 hours.
## Dose Adjustments
* **Renal Impairment:** Dose adjustments are often necessary. In patients with severe renal impairment, increased doses may be required due to impaired renal excretion of the drug. However, response may be blunted. Careful titration is essential.
* **Hepatic Impairment:** Dose reduction may be necessary, as furosemide is metabolized in the liver and can exacerbate hepatic encephalopathy.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides
## Adverse Effects
* **Electrolyte Imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration and Hypotension:** Especially with rapid diuresis or high doses.
* **Ototoxicity:** Hearing loss (often reversible, especially with rapid IV administration or high doses).
* **Hyperglycemia:** Can worsen glycemic control in diabetic patients.
* **Hyperuricemia:** Can precipitate gout.
* **Dizziness, lightheadedness.**
* **Rash, photosensitivity.**
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **NSAIDs:** May reduce the natriuretic and diuretic effect of furosemide and increase the risk of nephrotoxicity.
* **ACE Inhibitors/ARBs:** Increased risk of severe hypotension and hyperkalemia.
* **Digoxin:** Hypokalemia induced by furosemide increases the risk of digoxin toxicity.
* **Lithium:** Furosemide can decrease lithium clearance, increasing lithium levels and toxicity risk.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Antihypertensives:** Additive hypotensive effects.
## Monitoring
* **Electrolytes:** Serum electrolytes (sodium, potassium, chloride, magnesium, calcium) especially with initiation, dose changes, or prolonged therapy.
* **Renal function:** Serum creatinine and BUN.
* **Fluid balance:** Daily weights, intake and output.
* **Blood pressure:** Monitor for hypotension.
* **Blood glucose:** In patients with diabetes.
* **Uric acid:** In patients prone to gout.
* **Hearing:** Assess for tinnitus or hearing impairment.
## Clinical Pearls
* Furosemide is most effective when taken on an empty stomach, but may be taken with food or milk if gastric irritation occurs.
* Oral furosemide is generally absorbed erratically, and there is significant interindividual variability.
* Patients on high-dose furosemide or with significant electrolyte losses may require potassium or magnesium supplementation.
* Rapid IV administration can increase the risk of ototoxicity. Infuse slowly (e.g., over 30-60 minutes) or as an infusion.
* IV furosemide is generally considered more potent than oral furosemide on a milligram-for-milligram basis (e.g., a 1:2 ratio of IV to PO is often used).
* In patients with refractory edema, continuous IV infusion or frequent dosing may be more effective than bolus doses.
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*This information is intended for healthcare professionals and does not substitute for professional medical advice. Always verify current prescribing information with the official product labeling and institutional guidelines.*
