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# Furosemide
## Overview
Furosemide is a loop diuretic used to treat edema associated with heart failure, liver disease, and kidney disease, including the nephrotic syndrome. It is also used to treat hypertension, although it is not a first-line agent for this indication unless edema is also present.
## Primary Indications
* Edema (e.g., congestive heart failure, cirrhosis, renal disease)
* Hypertension (when edema is also present)
## Adult Dosing
* **Edema:**
* **Oral:** The typical starting dose is 20 mg to 80 mg once daily. Doses can be increased by 20 mg to 40 mg every 6 to 8 hours as needed. The usual maintenance dose is 40 mg to 120 mg daily, but doses up to 600 mg daily have been used in severe cases.
* **Intravenous (IV) or Intramuscular (IM):** The typical starting dose is 20 mg to 40 mg once daily. If insufficient response, doses can be increased by 20 mg every 2 hours or by 40 mg every 4 hours. The maximum daily IV dose is generally considered 200 mg, but higher doses may be used under specialist supervision.
* **Hypertension:**
* **Oral:** 40 mg twice daily. Usually used in combination with other antihypertensives.
## Pediatric Dosing
* **Edema:**
* **Oral:** 1 mg/kg/dose to 2 mg/kg/dose every 6 hours. The maximum daily dose is 6 mg/kg.
* **Intravenous (IV) or Intramuscular (IM):** 1 mg/kg/dose every 6 hours. If insufficient response, doses can be increased to 2 mg/kg/dose. The maximum dose is 6 mg/kg per day.
## Dose Adjustments
* **Renal Impairment:** Dose may need to be increased in patients with renal impairment due to decreased renal excretion. However, caution is advised as high doses can be nephrotoxic.
* **Hepatic Impairment:** Caution is advised; dose adjustments may be necessary.
## Contraindications
* Anuria
* Hypersensitivity to furosemide or sulfonamides
## Adverse Effects
Common: Dizziness, lightheadedness, orthostatic hypotension, fatigue, muscle cramps, electrolyte imbalances (hypokalemia, hyponatremia, hypochloremia), dehydration, hyperglycemia, hyperuricemia.
Serious: Ototoxicity (especially with rapid IV administration or high doses), severe hypotension, Stevens-Johnson syndrome, toxic epidermal necrolysis, agranulocytosis, aplastic anemia.
## Key Drug Interactions
* **Aminoglycosides:** Increased risk of ototoxicity and nephrotoxicity.
* **ACE inhibitors/ARBs:** Increased risk of hypotension and renal dysfunction, particularly in volume-depleted patients.
* **Corticosteroids:** Increased risk of hypokalemia.
* **Digoxin:** Increased risk of digoxin toxicity due to furosemide-induced hypokalemia.
* **NSAIDs:** May reduce the diuretic and antihypertensive effect of furosemide and increase the risk of renal impairment.
* **Lithium:** Furosemide can decrease lithium clearance, leading to increased serum lithium levels and risk of toxicity.
* **Warfarin:** Furosemide can displace warfarin from protein-binding sites, potentially increasing its anticoagulant effect.
## Monitoring
* Electrolytes (sodium, potassium, chloride)
* Renal function (BUN, creatinine)
* Blood pressure
* Urine output
* Glucose levels (especially in diabetics)
* Hearing (auditory assessment if concerns arise)
## Clinical Pearls
* Administer oral furosemide in the morning to minimize nocturia.
* For IV administration, slow infusion rates (e.g., over 30-60 minutes) are preferred to reduce the risk of ototoxicity.
* Monitor for signs of dehydration and electrolyte depletion, especially in elderly or debilitated patients.
* Patients with edema may require higher doses than those treated for hypertension.
* The bioavailability of oral furosemide can be variable; consider switching to IV if oral administration is ineffective.
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*Please verify the current prescribing information for the most up-to-date and comprehensive details.*
