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## Furosemide (Lasix)
### Overview
Furosemide is a potent loop diuretic used to treat edema associated with heart failure, liver disease, and renal disease, including nephrotic syndrome. It is also used to treat hypertension, although it is not typically a first-line agent for this indication alone.
### Primary Indications
* Edema (congestive heart failure, cirrhosis, renal disease, nephrotic syndrome)
* Hypertension (adjunctive therapy)
### Adult Dosing
* **Edema:**
* Oral: Initial dose 20-80 mg once daily. May be increased by 20-40 mg every 6-8 hours as needed. Usual maintenance dose is 40-120 mg once daily. Doses up to 600 mg/day have been used in severe cases, but higher doses may not increase efficacy and increase risk of adverse effects.
* Intravenous (IV) or Intramuscular (IM): Initial dose 20-40 mg once daily. May be increased by 20 mg every 2 hours as needed. May be administered as a continuous infusion at a rate of 4 mg/hour after an initial bolus dose.
* **Hypertension:**
* Oral: 40 mg twice daily. Often used in combination with other antihypertensives.
### Pediatric Dosing
* **Edema:**
* Oral: 1-2 mg/kg/dose once or twice daily. Maximum dose 6 mg/kg/day.
* IV/IM: 1 mg/kg/dose once daily. Maximum dose 6 mg/kg/day. Higher doses may be needed in premature infants.
### Dose Adjustments
* **Renal Impairment:** Furosemide is renally excreted. Dosage may need to be increased in renal insufficiency, but monitoring for ototoxicity and other adverse effects is crucial. In patients with significant renal impairment, higher doses may be required, and continuous infusion may be more effective than intermittent boluses.
* **Hepatic Impairment:** Furosemide clearance may be reduced in hepatic cirrhosis. Monitor for electrolyte imbalances and fluid status closely.
### Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides
### Adverse Effects
* Electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia, hypomagnesemia, hypocalcemia)
* Dehydration
* Hypotension
* Ototoxicity (especially with rapid IV administration or high doses, often reversible)
* Hyperuricemia (can precipitate gout)
* Hyperglycemia
* Dizziness, lightheadedness
* Rash, photosensitivity
### Key Drug Interactions
* **Aminoglycosides and other ototoxic drugs:** Increased risk of ototoxicity.
* **NSAIDs:** May decrease the diuretic and antihypertensive effect of furosemide and increase the risk of renal impairment.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Risk of digoxin toxicity increased by furosemide-induced hypokalemia.
* **Lithium:** Furosemide can decrease lithium clearance, increasing the risk of lithium toxicity.
* **Antihypertensives:** Additive hypotensive effect.
### Monitoring
* Electrolytes (sodium, potassium, chloride, magnesium, calcium)
* Renal function (BUN, creatinine)
* Fluid status (weight, intake/output)
* Blood pressure
* Hearing (especially with high doses or IV administration)
* Blood glucose
### Clinical Pearls
* Furosemide's onset of action is rapid: 30-60 minutes orally, 5-15 minutes IV/IM. Duration is typically 4-6 hours.
* To minimize nocturia, administer the last dose of the day no less than 4-6 hours before bedtime.
* Monitor for signs of hypokalemia (muscle weakness, cramps, arrhythmias) and consider potassium supplementation or potassium-sparing diuretics if clinically indicated.
* Rapid IV administration can increase the risk of ototoxicity and hypotension.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making therapeutic decisions.*
