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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium and chloride in the thick ascending limb of the Loop of Henle. This leads to increased excretion of water, sodium, chloride, potassium, 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 (usually in combination with other antihypertensives)
## Adult Dosing
* **Edema:** Initial dose is typically 20-80 mg orally once or twice daily. Doses can be increased by 20-40 mg every 6-8 hours as needed. The usual maintenance dose is 20-80 mg daily. Doses up to 600 mg/day have been used in severe cases, but higher doses increase the risk of adverse effects.
* **Hypertension:** Initial dose is typically 40 mg orally twice daily. It is generally not recommended as a first-line agent for hypertension alone.
* **IV/IM Dosing:** For patients who are unable to take oral medications or require more rapid diuresis, doses are typically half the oral dose. Initial dose 20-40 mg IM or IV. Subsequent doses may be 20-80 mg. Doses may be given every 6-12 hours. In severe, acute pulmonary edema, rapid IV administration of 20-40 mg may be considered.
## Pediatric Dosing
* **Edema:** 1-2 mg/kg/dose orally every 6-12 hours. Maximum 6 mg/kg/day.
* **IV/IM Dosing:** 1 mg/kg/dose IV or IM every 6-12 hours. Maximum 6 mg/kg/day.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in renal impairment due to decreased efficacy. However, caution is advised due to increased risk of ototoxicity and electrolyte imbalances. Monitor closely.
* **Hepatic Impairment:** Dose may need to be reduced due to increased bioavailability. Monitor fluid and electrolyte status closely.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides
* Hepatic coma or severe electrolyte depletion
## Adverse Effects
* **Electrolyte Imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration:** Dizziness, hypotension, orthostatic hypotension.
* **Ototoxicity:** Hearing impairment, tinnitus (especially with rapid IV administration or high doses).
* **Metabolic:** Hyperuricemia, hyperglycemia, increased cholesterol and triglycerides.
* **Renal:** Increased BUN and creatinine.
* **Gastrointestinal:** Nausea, diarrhea, abdominal pain.
* **Dermatologic:** Rash, photosensitivity.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, leading to increased lithium levels and toxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effect.
* **Potassium-Sparing Diuretics:** May be used to counteract furosemide-induced hypokalemia, but requires careful monitoring.
* **Antihypertensives:** Additive hypotensive effect.
## Monitoring
* **Fluid and Electrolytes:** Monitor serum electrolytes (sodium, potassium, chloride, magnesium, calcium) and fluid balance (intake/output, weight) regularly, especially during initiation or dose changes.
* **Renal Function:** Monitor BUN and serum creatinine.
* **Blood Pressure:** Monitor blood pressure, especially for orthostatic changes.
* **Hearing:** Assess for tinnitus or hearing loss.
* **Blood Glucose:** Monitor in patients with diabetes.
* **Uric Acid:** Monitor in patients with a history of gout.
## Clinical Pearls
* Administer oral furosemide with or without food.
* For IV administration, give slowly over 30-60 minutes unless in acute pulmonary edema. Rapid IV administration is associated with increased risk of ototoxicity.
* Furosemide is a potent diuretic. Initiate at the lowest effective dose and titrate based on patient response and tolerability.
* Oral administration is generally preferred for chronic management.
* Consider dietary potassium supplementation or potassium-sparing diuretics to manage hypokalemia.
**Disclaimer:** This information is intended for clinical pharmacists and is not a substitute for the official prescribing information or a comprehensive drug reference. Always consult the most current product monograph and/or local institutional protocols for complete and up-to-date information before making any prescribing or clinical decisions.
