Furosemide

# Furosemide ## Overview - **Classification**: Loop Diuretic (Sulfonamide derivative) - **Mechanism**: Inhibits the Na+-K+-2Cl− cotransporter (NKCC2) in the ascending limb of the loop of Henle. - Leads to rapid and potent diuresis and natriuresis. ## Primary Indications 1. **Edema**: Management of edema associated with heart failure, liver cirrhosis, or renal disease. 2. **Hypertension**: Primarily used in patients with resistant hypertension or volume overload. 3. **Acute Pulmonary Edema**: Rapid reduction of circulatory volume and preload. ## Adult Dosing ### Standard Dosing **Edema** (Initial Treatment) - **Dose**: **20 mg to 80 mg** - **Frequency**: Once daily or twice daily - **Route**: Oral (PO) - **Maximum Daily Dose**: Typically **600 mg**; higher doses used rarely. **Acute Pulmonary Edema/Acute Decompensated Heart Failure (ADHF)** - **Dose**: **20 mg to 40 mg** - **Frequency**: Single dose, repeated within 1-2 hours if needed. - **Route**: Intravenous (IV) - **Continuous Infusion**: **0.1 mg/kg/hr up to 40 mg/hr** (for acute settings). ### Dose Adjustments - **Renal Impairment (CrCl < 30 mL/min)**: Higher doses may be required for effectiveness. - **Renal Impairment (Dialysis)**: May need up to **200 mg IV** as a single dose (monitor closely). - **Hepatic Impairment (Cirrhosis)**: Initiate lower doses and titrate slowly; risk of hepatic encephalopathy increased. - **Elderly Patients**: Start at the lower end of the dosing range (e.g., **20 mg** PO) due to reduced renal function and dehydration risk. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose (Edema)**: **1 mg/kg/dose** - **Frequency**: Every 12 to 24 hours - **Maximum**: No more than 1 mg/kg/dose. - **Special Notes**: Risk of nephrocalcinosis and ototoxicity is higher. ### Infants (1-12 months) - **Dose (Edema)**: **1 mg/kg/dose** - **Frequency**: Every 6 to 12 hours - **Maximum**: **6 mg/kg/day** ### Children (1-12 years) - **Oral Dose (Edema)**: **2 mg/kg/dose** (initial) - **Frequency**: Once daily, increasing up to every 6-12 hours. - **Maximum**: **6 mg/kg/day** or **40 mg/dose** (whichever is less). ### Adolescents (13-18 years) - **Dose**: Use adult dosing (start with **20 mg to 40 mg** PO). - **Maximum**: Follow adult maximum limits (**600 mg/day**). ## Safety Information ### Contraindications - **Absolute**: Anuria (lack of urine output). - **Absolute**: Hypersensitivity to furosemide or sulfonamide derivatives. - **Relative**: Severe electrolyte depletion (e.g., severe hypokalemia or hyponatremia). ### Common Adverse Effects - **Very Common (>10%)**: Dehydration, Hypokalemia, Metabolic alkalosis. - **Common (1-10%)**: Dizziness, Ototoxicity (transient or permanent), Hyperuricemia. - **Serious but Rare**: Aplastic anemia, Stevens-Johnson Syndrome (SJS), Renal failure. ### Key Drug Interactions - **Aminoglycoside Antibiotics (e.g., Gentamicin)**: Increased risk of ototoxicity and nephrotoxicity. - **Digoxin**: Hypokalemia induced by furosemide can potentiate digoxin toxicity (arrhythmias). - **Lithium**: Furosemide reduces lithium clearance, leading to increased lithium levels and toxicity; monitor levels closely. - **NSAIDs (Nonsteroidal Anti-inflammatory Drugs)**: Can blunt diuretic effect and increase risk of renal toxicity. ## Monitoring & Follow-up - **Before Treatment**: Baseline electrolytes (Na, K, Mg, Ca), BUN, creatinine, urine output. - **During Treatment**: Monitor electrolytes and renal function (BUN/Cr) **daily** during IV therapy, then **weekly** or **monthly** with chronic PO therapy. - **Clinical Signs**: Monitor weight, orthostatic hypotension, extremity edema, and signs of hearing impairment. - **Target**: Maintain serum Potassium **>4.0 mEq/L**. ## Clinical Pearls - 💡 **Tip 1**: IV administration should be slow (over 1 to 2 minutes) to minimize the risk of ototoxicity. - 💡 **Tip 2**: If switching from IV to PO, the PO dose is often **double** the IV dose (e.g., 40 mg IV $\approx$ 80 mg PO). - 💡 **Tip 3**: Take earlier in the day to prevent nocturia; inform patients of diuretic effect within 1 hour. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.