What are the contraindications for Lasix (furosemide) in patients with impaired renal function, hepatic cirrhosis, hypokalemia, or a history of allergic reactions to sulfonamides?

Contraindications of Furosemide (Lasix)

Furosemide is absolutely contraindicated in patients with anuria, and should be discontinued immediately in cases of severe hyponatremia (serum sodium <120 mmol/L), progressive renal failure, worsening hepatic encephalopathy, or severe hypokalemia (<3 mmol/L). 1, 2

Absolute Contraindications

Anuria

• Furosemide must not be administered to patients with anuria, as the drug requires urinary excretion to reach its site of action in the loop of Henle and cannot be effective without urine production 1, 3, 2

Severe Electrolyte Disturbances

• Severe hyponatremia (serum sodium <120-125 mmol/L) is an absolute contraindication requiring immediate discontinuation of all diuretics 1, 3
• Severe hypokalemia (<3 mmol/L) mandates stopping furosemide specifically, though aldosterone antagonists may be continued 1, 3
• Severe hyperkalemia (>6 mmol/L) in the context of aldosterone antagonist therapy may require stopping the aldosterone antagonist rather than furosemide 1, 4

Marked Hypovolemia and Hypotension

• Systolic blood pressure <90-100 mmHg without circulatory support is a contraindication, as furosemide will worsen hypoperfusion and precipitate cardiogenic shock 3
• Marked hypovolemia must be corrected before initiating furosemide therapy 1, 3, 2

Relative Contraindications Requiring Extreme Caution

Hepatic Encephalopathy

• Overt or worsening hepatic encephalopathy in cirrhotic patients is generally a contraindication to diuretic therapy, as furosemide can precipitate or worsen encephalopathy 1, 5
• Furosemide-induced coma occurred in 11.6% of cirrhotic patients in prospective monitoring, with higher frequency in those with prior hepatic encephalopathy 5

Renal Impairment

• Caution is required when starting furosemide in patients with renal impairment, though no specific creatinine threshold is definitively established in guidelines 1
• Progressive renal failure or acute kidney injury requires immediate discontinuation 1, 3
• Furosemide does not prevent or treat acute kidney injury and may increase mortality when used for this purpose 6

Sulfonamide Allergy

• Patients allergic to sulfonamides may also be allergic to furosemide, as it is a sulfonamide derivative 2
• Cross-reactivity should be considered before administration 2

Urinary Retention

• In patients with severe urinary retention (bladder emptying disorders, prostatic hyperplasia, urethral narrowing), furosemide can cause acute urinary retention due to increased urine production 2
• These patients require careful monitoring, especially during initial treatment 2

Critical Clinical Situations Requiring Immediate Discontinuation

Incapacitating Muscle Cramps

• Severe or incapacitating muscle cramps require dose reduction or complete discontinuation of diuretics 1, 3
• Albumin infusion may relieve symptoms in cirrhotic patients 1

Metabolic Complications

• Hypochloremic alkalosis with severe symptoms requires drug withdrawal 2
• Symptomatic hyperuricemia or gout precipitation, though rare, may necessitate discontinuation 2

Special Population Considerations

Cirrhotic Patients

• In cirrhosis, 51.2% of patients experienced adverse reactions to furosemide, with 24% classified as severe 5
• Higher total doses, hyperbilirubinemia, prolonged prothrombin time, and longer hospital stays were associated with higher frequencies of adverse reactions 5
• Diuretics should be used with extreme caution in cirrhotic patients with renal impairment, hyponatremia, or potassium disturbances 1

Diabetic Patients

• Furosemide may increase blood glucose levels and precipitate diabetes mellitus, requiring careful monitoring 2
• Glucose tolerance tests may show abnormalities during therapy 2

Patients Receiving Radiocontrast

• In patients at high risk for radiocontrast nephropathy, furosemide can lead to higher incidence of renal function deterioration compared to IV hydration alone 2

Monitoring Requirements to Identify Developing Contraindications

• Frequent measurements of serum creatinine, sodium, and potassium should be performed during the first weeks of treatment 1, 2
• Daily weights should be monitored, with maximum target loss of 0.5 kg/day without edema and 1 kg/day with peripheral edema 1, 3
• Signs of fluid or electrolyte imbalance include dryness of mouth, thirst, weakness, lethargy, drowsiness, restlessness, muscle cramps, hypotension, oliguria, tachycardia, or arrhythmia 2

Common Pitfalls to Avoid

• Never use furosemide expecting it to improve hemodynamics in hypotensive patients—it will worsen tissue perfusion 3
• Do not escalate furosemide beyond 160 mg/day in cirrhosis—this indicates diuretic resistance requiring alternative strategies like large-volume paracentesis 1, 3
• Avoid combining furosemide with ethacrynic acid due to additive ototoxicity risk 2
• Exercise caution with aminoglycoside antibiotics, especially with impaired renal function, due to increased ototoxicity 2