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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) associated with heart failure, liver disease, and kidney disease, including nephrotic syndrome. It is also used to treat high blood pressure, alone or in combination with other antihypertensives.
## Primary Indications
* Edema associated with congestive heart failure (CHF)
* Edema associated with liver cirrhosis
* Edema associated with renal disease (including nephrotic syndrome)
* Hypertension
## Adult Dosing
* **Edema:**
* Oral: 20-80 mg once daily. If inadequate response, dose may be increased by 20-40 mg every 6-8 hours or given in divided doses. Typical maintenance doses range from 40-80 mg daily. Doses up to 600 mg daily have been used in severe cases.
* Intravenous (IV) or Intramuscular (IM): 20-40 mg once daily. If inadequate response, dose may be increased by 20 mg every 2 hours.
* **Hypertension:**
* Oral: 40 mg twice daily. May be used as monotherapy or in combination.
* **General:** Doses should be individualized based on patient response and need.
## Pediatric Dosing
* **Edema and Hypertension:**
* Oral: 1-2 mg/kg/dose once daily. If inadequate response, dose may be increased by 1 mg/kg/dose every 6-8 hours. Do not exceed 6 mg/kg/dose.
* IV or IM: 1 mg/kg/dose. If inadequate response, dose may be increased by 1 mg/kg/dose every 2 hours. Do not exceed 6 mg/kg/dose.
* **Note:** Dosing in neonates can be complex due to immature renal function. Consult specific pediatric guidelines.
## Dose Adjustments
* **Renal Impairment:** Furosemide is renally excreted. Dose may need to be increased in patients with renal impairment to achieve a similar diuretic effect. However, caution is advised as higher doses can be associated with increased toxicity. In severe renal impairment, doses may exceed typical maximums but require careful monitoring.
* **Hepatic Impairment:** Monitor electrolytes and fluid status closely. Dose adjustments may be necessary.
## Contraindications
* Anuria
* Known hypersensitivity to furosemide or sulfonamides (due to potential cross-sensitivity)
* Severe electrolyte depletion (e.g., hyponatremia, hypokalemia)
## Adverse Effects
* **Common:** Dizziness, lightheadedness, dehydration, hypokalemia, hyponatremia, hypotension, increased urination, hyperuricemia (can precipitate gout).
* **Less Common/Serious:** Ototoxicity (especially with rapid IV administration or high doses), hyperglycemia, pancreatitis, cholestatic jaundice, blood dyscrasias (anemia, leukopenia, thrombocytopenia), severe allergic reactions.
## Key Drug Interactions
* **Aminoglycosides/Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **ACE Inhibitors/ARBs:** Increased risk of hypotension and renal impairment, especially in volume-depleted patients.
* **NSAIDs:** May reduce the diuretic and antihypertensive effect of furosemide.
* **Lithium:** Furosemide can decrease lithium clearance, increasing the risk of lithium toxicity.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Hypokalemia induced by furosemide increases the risk of digoxin toxicity.
## Monitoring
* **Electrolytes:** Monitor serum electrolytes (sodium, potassium, chloride, magnesium, calcium) regularly, especially with higher doses or prolonged therapy.
* **Fluid Balance:** Monitor intake and output, daily weights, and signs of dehydration or fluid overload.
* **Renal Function:** Monitor BUN and creatinine.
* **Blood Pressure:** Monitor for hypotension.
* **Auditory Function:** Assess for tinnitus or hearing loss, particularly with high doses or rapid IV administration.
## Clinical Pearls
* Furosemide is a potent diuretic; start with the lowest effective dose.
* Administer oral furosemide on an empty stomach for better absorption, but it can be taken with food or milk if gastric upset occurs.
* IV administration can be given as a bolus or infusion. Infusion may reduce the risk of ototoxicity compared to bolus dosing at high concentrations.
* Rapid IV administration can lead to ototoxicity.
* Electrolyte disturbances, particularly hypokalemia, are common and can have serious consequences. Patient education on potassium-rich foods is important.
* Monitor for signs of dehydration and electrolyte imbalances.
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**Disclaimer:** This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and local protocols before making any clinical decisions. Dosing and recommendations may vary based on individual patient factors and institutional guidelines.
