When should Lasix (furosemide) be used?

When to Use Lasix (Furosemide)

Furosemide should be used for the treatment of edema associated with congestive heart failure, cirrhosis of the liver, renal disease including nephrotic syndrome, and for acute pulmonary edema when rapid onset of diuresis is required. 1

Primary Indications

1. Edema Management

• Heart Failure: First-line diuretic for fluid overload in heart failure patients
• Cirrhosis with Ascites: Used in combination with spironolactone (typically in a 40mg:100mg ratio) 2
• Renal Disease: Including nephrotic syndrome and other conditions causing fluid retention
• Acute Pulmonary Edema: Intravenous administration when rapid diuresis is needed 1

2. Route of Administration Considerations

• Oral: Preferred for chronic management when gastrointestinal absorption is intact
• Intravenous: Reserved for:
  • Emergency situations requiring rapid diuresis (e.g., acute pulmonary edema)
  • Patients unable to take oral medications
  • Cases where gastrointestinal absorption is impaired 1

Dosing Strategies

For Cirrhosis with Ascites

• Start with combination therapy: furosemide 40 mg + spironolactone 100 mg once daily in the morning
• Doses can be increased every 3-5 days while maintaining the 40:100 ratio if weight loss is inadequate
• Maximum doses typically 160 mg furosemide and 400 mg spironolactone daily 2
• Single morning dosing maximizes compliance 2

For Congenital Nephrotic Syndrome

• Use only in cases of intravascular fluid overload (evidenced by good peripheral perfusion and high blood pressure)
• Consider IV bolus of 0.5-2 mg/kg at the end of albumin infusions
• For severe edema: 0.5-2 mg/kg per dose up to six times daily (maximum 10 mg/kg/day)
• High doses (>6 mg/kg/day) should not be given for periods longer than 1 week 2

For Heart Failure

• Initial dose of 20-40 mg IV bolus for acute presentations
• Dose can be increased according to renal function and history of chronic diuretic use 3

Monitoring Requirements

1. Fluid Status:

   • Daily weight
   • Urine output
   • Clinical signs of fluid overload or depletion

2. Laboratory Parameters:

   • Electrolytes (particularly sodium, potassium, magnesium)
   • Renal function (BUN, creatinine)
   • Regular monitoring during first month of treatment 3

3. Discontinuation Criteria:

   • Serum sodium below 125 mmol/L
   • Anuria
   • Marked hypovolemia 2, 3

Special Considerations and Cautions

Combination Therapy

• In cirrhosis: Combine with spironolactone for synergistic effect and to maintain normokalemia 2
• In stable patients: Can be given with thiazide or potassium-sparing diuretics with appropriate monitoring 2
• For potassium-sparing effects, amiloride (10-40 mg/day) may be preferred over spironolactone in certain cases 2

Potential Adverse Effects

• Electrolyte disturbances (hypokalemia, hyponatremia, hypochloremia)
• Dehydration and hypotension
• Ototoxicity with high doses or rapid IV administration
• Hyperuricemia and gout
• Glucose intolerance

Contraindications/Cautions

• Anuria
• Severe hypovolemia
• Severe hyponatremia (serum sodium <120-125 mmol/L) 2
• Hepatic coma or severe electrolyte depletion

Practical Approach to Furosemide Use

1. Identify appropriate indication (edema from heart failure, cirrhosis, renal disease, or acute pulmonary edema)
2. Assess volume status and ensure patient is not hypovolemic
3. Check baseline electrolytes and renal function
4. Select appropriate dose based on condition and severity
5. Monitor response (diuresis, weight loss, symptom improvement)
6. Adjust dose based on response and laboratory parameters
7. Switch from IV to oral administration as soon as practical when using parenteral therapy

Remember that furosemide acts at the luminal surface of the ascending limb of the loop of Henle by inhibiting active chloride reabsorption, and its effectiveness is related to the concentration of the drug in urine rather than plasma levels 4.