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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic that inhibits the reabsorption of sodium and chloride in the ascending limb of the loop of Henle, leading to increased excretion of water, sodium, chloride, potassium, calcium, and magnesium.
## Primary Indications
* Edema associated with congestive heart failure (CHF), liver cirrhosis, and renal disease (including the nephrotic syndrome).
* Hypertension (used alone or in combination with other antihypertensives).
* Acute pulmonary edema.
## Adult Dosing
* **Edema:**
* Oral: Start with 20-80 mg once daily. The dose may be titrated upward by 20-40 mg every 6-8 hours as needed. For chronic edema, the dose should be adjusted to the lowest effective level. Doses up to 600 mg/day have been used in severe cases, but typically not recommended for routine use.
* Intravenous (IV)/Intramuscular (IM): Start with 20-40 mg once daily. If no response within 2 hours, a repeat dose of 20-40 mg may be given. Subsequent doses can be increased by 20 mg or 40 mg every 2 hours until the desired diuresis is achieved. For patients with severe renal impairment, higher doses may be required. Intermittent dosing (e.g., every 6-12 hours) is preferred. Continuous IV infusion may be used in some situations.
* **Hypertension:**
* Oral: 40 mg twice daily.
* **Acute Pulmonary Edema:**
* IV/IM: 20-40 mg administered as a single dose. If adequate response is not obtained within 30 minutes, a second dose of 20-40 mg may be administered.
## Pediatric Dosing
* **Edema/Hypertension:**
* Oral: 1-2 mg/kg/dose once or twice daily. Maximum dose: 6 mg/kg/day.
* IV/IM: 1 mg/kg/dose. Maximum dose: 20 mg/dose for neonates and infants younger than 2 months; 40 mg/dose for older infants and children. Doses can be repeated every 6 hours if necessary.
## Dose Adjustments
* **Renal Impairment:** Dose adjustments are often necessary. Patients with severe renal impairment may require higher doses. Monitor for efficacy and toxicity closely.
* **Hepatic Impairment:** Use with caution. Electrolyte imbalances can precipitate hepatic coma.
## Contraindications
* Anuria.
* Known hypersensitivity to furosemide or sulfonamides.
## Adverse Effects
* **Electrolyte imbalances:** Hypokalemia, hyponatremia, hypochloremia, hypocalcemia, hypomagnesemia.
* **Dehydration and hypotension.**
* **Ototoxicity:** Especially with rapid IV administration or high doses.
* **Hyperuricemia:** May precipitate gout.
* **Hyperglycemia.**
* **Dermatologic reactions:** Rash, photosensitivity.
* **Aplastic anemia, agranulocytosis, thrombocytopenia, leukopenia.**
## Key Drug Interactions
* **Aminoglycosides/Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **Antihypertensives:** Additive hypotensive effects.
* **NSAIDs:** May reduce natriuretic and diuretic effects.
* **Lithium:** Reduced renal clearance, increased risk of lithium toxicity.
* **Corticosteroids:** Increased risk of hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium).
* Renal function (BUN, creatinine).
* Fluid status (weight, intake/output, signs of edema).
* Blood pressure.
* Hearing.
* Blood glucose and uric acid levels (in susceptible patients).
## Clinical Pearls
* Rapid IV administration can lead to ototoxicity and flushing. Administer IV furosemide slowly, typically over 20-60 minutes, or as a continuous infusion.
* Hypokalemia is a common and significant adverse effect; monitor closely and consider potassium supplementation or potassium-sparing diuretics if indicated.
* Patients with severe renal impairment may be resistant to furosemide and require higher doses or alternative diuretic strategies.
* For patients with significant edema, weigh daily and adjust dose to achieve a consistent weight loss of 1-2 kg/day to avoid excessive fluid loss.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before administering any medication. Dosing may vary based on individual patient factors and local protocols.*
