Furosemide (Lasix) Drug Study

Furosemide [Fu-RO-se-mide]  

Brand names

• Lasix (commonly used) 
• Furoscix (subcutaneous) 
• Lasix ONYU (subcutaneous infusion form) 
• Apo-Furosemide 
•  Frusemide 
• Diural or Impugan. 

Therapeutic classification 

Diuretic and antihypertensive. 

Pharmacological classification

• Loop diuretic i.e. high-ceiling  

• sulfonamide derivative, also known as an anthranilic acid derivative. 

Compared to other classes of Diuretics,  these drugs are the most efficient in the mobility of  Na⁺  and Cl⁻from the body via excessive urinary output. Amongst all the diuretics in this class, Furosemide is the most commonly used because of its lesser side effects as compared to Ethacrynic acid.  

Therapeutic uses/Indications: 

• Edema associated with CHF (congestive heart failure) 

• Liver cirrhosis  

•  Nephritic syndrome (in adults and pediatric patients). 

• Hypertension  (primarily oral form).   

• IV form in Acute pulmonary edema as Adjunctive therapy  

Mechanism of Action

Furosemide inhibits sodium and chloride ions reabsorption in the thick ascending limb of the loop of Henle, particularly in the proximal and distal, blocking the sodium-potassium-chloride cotransporter (NKCC2). This ultimately leads to elevated excretion of water, sodium, chloride, magnesium, calcium, and other major electrolytes, which further results in diuresis (increased urine output) and a significant reduction in fluid overload. 

Dosage and administration 

Dosage varies by  

•  Indication 
• Route 
• Patient response, and condition (e.g., adjust for renal function).  
• Oral (tablets or solution) is utilized for edema 
• Adults — initial 20–80 mg/day administered as a single dose, dosage may be repeated or increased by 20–40 mg every 6–8 hours as required (max often 600 mg/day in severe cases).  
• Maintenance dose varies. Pediatrics — 1–2 mg/kg (not to exceed 6 mg/kg).   
• Oral dosage for hypertension: Adults — 20–80 mg/day, often the dosage is divided.   
•  IV/IM for rapid effect; Adults dose js — 20–40 mg initially; may repeat or infuse. Pediatric dosage regimen— 1 mg/kg.   
• Subcutaneous dosage form (e.g., Furoscix): Specific device-delivered doses form for chronic Heart Failure edema (e.g., 80 mg total over Specified5 hours).   
• Administer the oral dosage form with or without food; IV slowly to avoid any ototoxicity. 

Preparation of a dosage form   

• Oral Tablets dosage form is available in the following mg (20 mg, 40 mg) 
• Dispensing oral solutions 10 mg/m.  
• No special preparation is needed despite standard dispensing.   
• Injectable Solution as 10 mg/m in vials/syringes for administration via IV/IM; dilute if needed for dosage infusion (e.g., in D5W or  NS, but do check compatibility).   
• Subcutaneous: Pre-filled, on-body infusor devices (e.g., Furoscix or Lasix ONYU) — no manual preparation; apply as instructed for auto-delivery. 

Pharmacokinetics 

Absorption: 

• Oral bioavailability ~50–64% (variable and is reduced in Heart failure or edema) 
• Oral solutions are absorbed quite faster than tablets. IV/IM: nearly 100%.   

Onset  

• Oral — 30–60 min 
•  IV — tablets 
• Peak effect 1–2 hours for oral 
•  0.5–1 hour IV.   

Duration

•  6–8 hours oral dosage form 
• ~2 hours IV dosage form 

Distribution 

Highly protein-bound (about 91–99%, mainly bound to albumin); reduced binding in elderly patients or hypalbuminemia.   

Metabolism 

Minimal because it is primarily excreted unchanged.   

Elimination

• Renal (mostly glomerular filtration and tubular secretion);  
• Half-life of furosemide is~2 hours (prolonged in renal impaired ir elderly).  
• Not significantly/completely removed by hemodialysis. 

Side Effects: Remember OH DANG (ototoxicity,  Hypotension,  Dehydration,  Allergic Reactions,  Nausea/Dizziness, Gout) 

• Common: Dehydration 
• Electrolyte imbalances 
• 4H’s (hypokalemia, hyponatremia, hypomagnesaemia, hypocalcemia) 
• Hypotension 
• Dizziness 
• Headache 
• Muscle cramps.   

Serious 

• Ototoxicity (especially high-dose/rapid IV), especially when used in combination with aminoglycoside antibiotics. Permanent damage is observed on continued use.  
• Severe hypokalemia leading to worsening arrhythmias

Note: This condition can be averted via proper usage of dietary potassium supplementation or via combination therapy with potassium-sparing diuretics 

• Gout (hyperuricemia), as it competes with uric acid on account of the biliary as well as renal secretory system, ultimately blocks its secretion, which leads to gouty attacks. 
• Hyperglycemia 
• Allergic reactions (in sulfa-sensitive patients) 
• Thrombocytopenia 

Drug interactions

• Potentiates ototoxicity when used with aminoglycosides I.e. cisplatin.   
• Increases lithium toxicity because of reduced clearance.   
• Hypokalemia risk increases with corticosteroids, amphotericin B, and other similar diuretics.   
• Reduced antihypertensive effect when used with NSAIDs (prostaglandin inhibition).   
• Increased and potentiated effects with other antihypertensives.   
• Antagonized when used along with probenecid (reduced secretion).   
• Monitor closely for co-administration with digoxin (hypokalemia increases toxicity). 

Usage   

Primarily used for symptomatic relief of “fluid-overload” and blood pressure maintenance in specified conditions. Start from the lowest effective dosage form; monitor the weight of the patient, electrolytes (especially electrolytes, calculate dose, renal function, and blood pressure without delay regularly. Reserve parenteral usage for when oral not feasible or when rapid action is essentially needed. High risk of severe electrolyte/fluid disturbances observed on routine use.  

Storage

• Store at room temperature,  keep away from excessive heat and away from children 
• For oral solutions, discard after 90days if left unused 
• For Injectable, store at low temperatures 20°C to 25°C (68°F to 77°F), DO NOT REFRIGERATE, UNTIL OR UNLESS SPECIFIED. 

Patient Education 

• Take as prescribed; do not stop all at once/abruptly.   
• Always check the product label before use 
• Expect excessive urination; take earlier in the day to avoid discomfort at night.   
• Report any signs of increased dehydration (dry mouth, thirst, weakness, dizziness), hearing changes or electrolyte issues 
• Maintain adequate potassium intake (e.g., via diet/supplements); avoid excessive intake of salt.   
• Weigh daily and report any sudden changes.   
• May cause dizziness; be cautious and rise slowly from sitting/lying.   
• Keep the provider of all medications informed, including OTC/herbals. 

Nursing Interventions

• Monitoring vital signs, it is essential while taking furosemide because it is a potent loop diuretic and excessive fluid loss occurs via enhanced urinary output. In addition to fluid loss, some essential electrolytes wash away from the body, leading to severe deficiency. Thus, it is essential to take the patient’s vitals. 
• Daily weights to assess kidney injury. Dehydration or any signs of excessive fluid loss. 
• Intake/output, and fluid balance closely for monitoring 4H’s (hypokalemia, hypomagnesaemia,  hypocalcemia, and hypoglycemia) 
• Frequent electrolyte panels (especially K+, Na+, Mg++, Ca++), BUN/creatinine, glucose, and uric acid.   
• Assess for signs of dehydration 
• Check for hypotension 
• Monitor ototoxicity (tinnitus, hearing loss).   
• Administer IV form slowly (e.g., 4 mg/min).   
• Ensure potassium supplementation.   
• Educate the patient on self-monitoring and provide complete education, and tell them when to seek help.   
• In HF/edema, monitor for worsening if the situation/symptoms (dyspnea, swelling).   
• For subcutaneous forms, foremost important is proper device application and site monitoring. 

Administration  

Administer earlier to avoid sleep disturbances and nocturia; it is recommended to give the oral dosage form with food or milk to significantly reduce G.I Disturbances. Take special care while administering IV solutions, D not push rapidly as it will cause ototoxicity. Consider administration of 20-40mg over 1-2mins for safety. 

Monitoring Electrolyte and Fluid Balance  

• Furosemide disturbs the electrolyte balance via enhanced urinary output; it is essential to notice and report oliguria if <30ml/hour. Monitor the patient’s Vitals on the same time everyday and closely monitor for any sign of dehydration,  weight loss or hypokalemia as these are the major side effects of furosemide. 

Management of complications 

• It is essential to educate patients to prevent falls as continuous use of furosemide leads to dizziness, postural hypotension, and weakness. It is recommended to educate patients on changing positions slowly to avoid risks of falls. 
• Be very cautious while taking patient history and report liver disease, gout, diabetes, or any kind of sulfonamide allergy because the risk of cross-sensitivity is higher. 
• Encourage potassium rich diet or potassium supplements to support potassium loss from the body.