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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium, chloride, and potassium in the ascending limb of the loop of Henle. This results in increased excretion of water, sodium, chloride, potassium, and other electrolytes.
## Primary Indications
* Edema associated with congestive heart failure (CHF)
* Edema associated with hepatic cirrhosis
* Edema associated with renal disease, including nephrotic syndrome
* Hypertension (adjunctive therapy)
## Adult Dosing
* **Edema:**
* Oral: 20-80 mg once daily. Doses may be increased by 20-40 mg every 6-8 hours as needed. Doses greater than 80 mg should be administered with caution.
* IV/IM: 20-40 mg once daily. If no response, the dose may be increased by 20 mg every 2 hours. Continuous infusion may be considered for refractory edema.
* **Hypertension:**
* Oral: 40 mg twice daily. Doses higher than 40 mg are generally not recommended for initial treatment of hypertension.
The maximum daily oral dose is typically 600 mg, but higher doses have been used under close medical supervision. Maximum IV doses are not clearly defined and depend on patient response and clinical situation.
## Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose every 6-12 hours. Doses may be increased by 1 mg/kg/dose every 6-8 hours as needed. Maximum dose: 6 mg/kg/day.
* IV/IM: 1 mg/kg/dose every 1-2 hours until desired response is achieved. Subsequent doses may be given every 6-12 hours. Continuous infusion: 0.1-0.2 mg/kg/hour.
## Dose Adjustments
* **Renal Impairment:** Dose adjustments may be necessary. Patients with severe renal impairment may require higher doses due to reduced renal clearance, but often have decreased diuretic response. Careful monitoring is crucial.
* **Hepatic Impairment:** Dose adjustments may be necessary. Monitor for electrolyte imbalances and fluid status closely.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides
## Adverse Effects
* **Electrolyte abnormalities:** Hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia.
* **Dehydration:** Volume depletion, hypotension.
* **Ototoxicity:** Tinnitus, hearing impairment (especially with rapid IV administration or high doses).
* **Metabolic:** Hyperglycemia, hyperuricemia (can precipitate gout).
* **Dermatologic:** Rash, photosensitivity.
* **Renal:** Increased BUN, creatinine.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effect of furosemide, and increase risk of renal impairment.
* **Lithium:** Decreased renal clearance of lithium, increasing risk of lithium toxicity.
* **Potassium-depleting agents (e.g., corticosteroids):** Additive risk of hypokalemia.
* **Thiazide diuretics:** Additive diuretic and natriuretic effects.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Fluid balance (intake and output, weight changes)
* Blood pressure
* Hearing (especially with high doses or rapid IV administration)
## Clinical Pearls
* Administer oral furosemide in the morning to minimize nocturia.
* If a dose is missed, take it as soon as remembered unless it is close to the time for the next dose.
* Monitor for signs and symptoms of electrolyte depletion (e.g., muscle cramps, weakness, dizziness).
* IV administration should be slow (over 30-60 minutes) to reduce the risk of ototoxicity. Avoid rapid IV push.
* Furosemide can be crushed and mixed with liquids or food for administration.
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**Disclaimer:** This information is intended for clinical pharmacists and healthcare professionals. It is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines for complete details and to ensure patient safety.
