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## Furosemide (Lasix)
### Overview
Furosemide is a potent loop diuretic used to treat fluid overload (edema) and hypertension.
### Primary Indications
* Edema associated with congestive heart failure (CHF), liver cirrhosis, and renal disease (including nephrotic syndrome).
* Hypertension (usually in combination with other antihypertensives).
* Acute pulmonary edema.
### Adult Dosing
* **Edema:**
* **Oral:** Start with 20-80 mg once or twice daily. The dose may be increased by 20-40 mg every day or every other day. Individualize dose based on response. Maximum single oral dose is typically 600 mg/day, but higher doses may be used under close supervision in specific situations.
* **Intravenous (IV) or Intramuscular (IM):** Start with 20-40 mg once. If no adequate diuresis occurs within 2 hours, a second dose of 40 mg may be given. If still no response, subsequent doses can be increased by 20 mg every 2 hours, or administered by continuous IV infusion. Maximum IV/IM dose is typically 600 mg/day, but higher doses may be used under close supervision.
* **Hypertension:**
* **Oral:** Start with 40 mg twice daily. Adjust dose as needed. Often used in combination therapy.
* **Acute Pulmonary Edema:**
* **IV:** 20-40 mg administered slowly over 30-60 minutes. If needed, repeat doses can be given every 2-4 hours.
### Pediatric Dosing
* **Edema and Hypertension:**
* **Oral:** 1-2 mg/kg/dose once daily. If needed, increase dose by 1-2 mg/kg every 6-8 hours. Maximum dose: 6 mg/kg/day.
* **IV or IM:** 1 mg/kg/dose once daily. If inadequate response, increase dose by 1 mg/kg every 2 hours. Maximum dose: 6 mg/kg/day. Continuous infusion may be used: 0.1 mg/kg/hour.
### Dose Adjustments
* **Renal Impairment:** In patients with significant renal impairment, higher doses may be required due to reduced GFR and altered drug metabolism. However, monitor closely for electrolyte imbalances and ototoxicity. Dose adjustments are generally based on clinical response and electrolyte levels.
* **Hepatic Impairment:** Use with caution. Dose may need to be reduced in patients with severe hepatic cirrhosis, especially if ascites is present, to avoid electrolyte disturbances and hepatic encephalopathy.
### Contraindications
* Anuria.
* History of hypersensitivity to furosemide or sulfonamides (cross-sensitivity may occur).
* Severe electrolyte depletion (e.g., hypokalemia, hyponatremia).
### Adverse Effects
* **Common:** Dizziness, lightheadedness, dehydration, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia), hyperuricemia, hyperglycemia.
* **Serious:** Ototoxicity (hearing loss, tinnitus, often reversible), hypotension, severe skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis), pancreatitis, blood dyscrasias, renal failure.
### Key Drug Interactions
* **Aminoglycosides/Other Ototoxic Drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May reduce diuretic and antihypertensive effect.
* **Lithium:** Furosemide can decrease lithium clearance, leading to increased lithium levels and toxicity.
* **Digoxin:** Hypokalemia induced by furosemide increases the risk of digoxin toxicity.
* **Antihypertensives:** Additive hypotensive effect.
* **Corticosteroids:** Increased risk of hypokalemia.
### Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium), BUN, creatinine, uric acid, and glucose at baseline and periodically during therapy.
* Fluid intake and output.
* Weight changes.
* Blood pressure.
* Hearing function (especially with high doses or prolonged use).
### Clinical Pearls
* Administer oral furosemide with food or milk to minimize GI upset.
* IV/IM administration should be slow to reduce the risk of ototoxicity and hypotension.
* Patients with significantly impaired renal function may require higher doses and closer monitoring.
* Furosemide can cause photosensitivity; advise patients to use sun protection.
* Regular monitoring of electrolytes is crucial, particularly potassium, to prevent arrhythmias and other complications.
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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 guidelines, and use your clinical judgment when making treatment decisions.*
