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# Furosemide (Lasix)
## Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) and high blood pressure. It works by inhibiting the reabsorption of sodium and chloride in the kidneys, leading to increased urine output.
## Primary Indications
* Edema associated with congestive heart failure, liver cirrhosis, and renal disease (including nephrotic syndrome).
* Hypertension (usually in combination with other antihypertensives).
* Acute pulmonary edema.
## Adult Dosing
* **Edema:** Initial dose is typically 20-80 mg orally once daily. Doses may be increased by 20-40 mg every 6-8 hours as needed. Doses up to 600 mg daily have been used in severe cases, but this requires careful monitoring. Maintenance doses are usually lower and may be given once or twice daily.
* **Hypertension:** Initial dose is 40 mg orally twice daily. Adjustments are based on response.
* **Acute Pulmonary Edema:** 20-40 mg intravenously (IV). Subsequent doses of 20 mg IV may be given every 2 hours as needed. Higher IV doses may be necessary in patients with impaired renal function or those who have not responded adequately.
## Pediatric Dosing
* **Edema/Hypertension:** 1-2 mg/kg orally once daily. Doses may be increased by 1-2 mg/kg every 6-8 hours. Maximum daily dose is 6 mg/kg.
* **IV/IM Dosing:** 1 mg/kg. Maximum 20 mg per dose, unless otherwise indicated by clinical response and physician order. Higher doses may be required in neonates and premature infants.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with renal impairment due to reduced drug excretion. However, caution is advised as higher doses may also increase the risk of ototoxicity. Consider IV administration for more predictable absorption.
* **Hepatic Impairment:** Caution is advised. Electrolyte imbalances can precipitate hepatic encephalopathy.
## Contraindications
* Anuria.
* Hypersensitivity to furosemide or sulfonamides.
* Hepatic coma or severe electrolyte depletion.
## Adverse Effects
* **Common:** Dizziness, lightheadedness, dehydration, hypokalemia, hyponatremia, hypochloremia, hyperuricemia, hyperglycemia.
* **Serious:** Hypotension, ototoxicity (hearing loss, tinnitus, often irreversible with high doses or rapid IV administration), Stevens-Johnson syndrome, exfoliative dermatitis, aplastic anemia, photosensitivity.
## Key Drug Interactions
* **Aminoglycosides, Cisplatin:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effect.
* **ACE Inhibitors/ARBs:** Increased risk of severe hypotension, particularly with initial doses or in volume-depleted patients.
* **Digoxin:** Increased risk of toxicity due to furosemide-induced hypokalemia.
* **Lithium:** Reduced renal clearance of lithium, increasing risk of lithium toxicity.
* **Antihypertensives:** Additive hypotensive effects.
* **Corticosteroids:** Increased risk of electrolyte disturbances (especially hypokalemia).
## Monitoring
* **Electrolytes:** Serum electrolytes (sodium, potassium, chloride) and bicarbonate.
* **Renal Function:** Serum creatinine and BUN.
* **Fluid Status:** Daily weights, intake and output.
* **Blood Pressure:** Monitor for hypotension.
* **Blood Glucose:** Especially in patients with diabetes.
* **Uric Acid:** Monitor for hyperuricemia.
* **Hearing:** Assess for tinnitus or hearing loss, particularly with high doses.
## Clinical Pearls
* Administer oral furosemide with food or milk to minimize gastrointestinal upset.
* If administered for edema, the timing of the dose should be adjusted to minimize nocturia and sleep disruption.
* Rapid IV administration can increase the risk of ototoxicity. Infuse slowly (e.g., 20 mg over 1-2 minutes or as an infusion).
* Monitor electrolytes closely, especially potassium. Potassium supplementation may be required.
* Be aware of the potential for cross-reactivity in patients with sulfonamide allergies.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant literature for complete details and to ensure patient safety.*
