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# Furosemide
## Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver cirrhosis, and renal disease, including nephrotic syndrome. It is also used to treat hypertension, usually in combination with other antihypertensives.
## Primary Indications
* Edema (congestive heart failure, hepatic cirrhosis, renal disease, including nephrotic syndrome)
* Hypertension
## Adult Dosing
**Edema:**
* **Oral:** 20-80 mg once daily. If a larger dose is needed, it can be given as a single dose or divided doses. The dose may be increased by 20-40 mg every 6-8 hours until desired response is obtained.
* **IV/IM:** 20-40 mg once daily. If a larger dose is needed, it can be given as a single dose or divided doses. The dose may be increased by 20 mg every 2 hours or 40 mg every 4 hours until desired response is obtained. Doses may reach 80-120 mg for severe cases.
* **Continuous IV Infusion:** 4 mg/hour. May increase by 1-2 mg/hour every 2 hours.
**Hypertension:**
* **Oral:** 40 mg twice daily. May be adjusted to 20-120 mg per day in divided doses.
**Maximum Oral Dose:** 600 mg/day (for patients with severe renal disease).
**Maximum IV/IM Dose:** Generally 120 mg/dose, but doses up to 200 mg have been used in specific situations.
## Pediatric Dosing
**Edema:**
* **Oral:** 1-2 mg/kg/dose every 6-12 hours. Maximum 6 mg/kg/day.
* **IV/IM:** 1 mg/kg/dose every 6-12 hours. Maximum 40 mg/dose or 1 mg/kg/dose, whichever is less. Higher doses up to 2 mg/kg/dose may be required in premature infants or those with severe edema.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased, especially in patients with severe renal impairment, as tolerance can develop. However, caution is advised as it can also worsen renal function.
* **Hepatic Impairment:** Monitor electrolytes closely. Dose reduction may be necessary.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides (caution due to potential cross-reactivity)
* Electrolyte depletion (e.g., hypokalemia, hyponatremia)
## Adverse Effects
Common adverse effects include dizziness, lightheadedness, weakness, hypokalemia, hyponatremia, dehydration, hypotension, and hyperuricemia. Less common but serious effects include ototoxicity (especially with rapid IV administration or high doses), hyponatremia, hypochloremia, metabolic alkalosis, hyperglycemia, and pancreatitis.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **NSAIDs:** May decrease diuretic and antihypertensive effects and increase risk of renal impairment.
* **Lithium:** Furosemide can decrease lithium clearance, increasing the risk of lithium toxicity.
* **Antihypertensives:** Additive hypotensive effects.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
## Monitoring
* Electrolytes (sodium, potassium, chloride)
* Renal function (BUN, creatinine)
* Fluid balance (intake and output, weight)
* Blood pressure
* Blood glucose (especially in diabetics)
* Uric acid levels
* Hearing (especially with high doses or IV administration)
## Clinical Pearls
* Administer IV furosemide slowly (over at least 30-60 minutes for doses >40mg) to reduce the risk of ototoxicity. Avoid rapid injection.
* Monitor for signs of hypokalemia (muscle cramps, weakness, arrhythmias) and consider potassium supplementation or potassium-sparing diuretics if necessary.
* Monitor for dehydration and hypotension.
* Patients may develop tolerance to the diuretic effect with chronic use, potentially requiring dose escalation.
* Loop diuretics can cause significant electrolyte and fluid losses, necessitating regular monitoring.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the official prescribing information and relevant clinical guidelines for the most current and complete details.*
