From the Guidelines
Lasix (furosemide) can cause several side effects, including hypokalemia, dehydration, electrolyte imbalances, dizziness, lightheadedness, and low blood pressure, as reported in a study published in 2021 1.
Common Side Effects
- Increased urination
- Dehydration
- Electrolyte imbalances (particularly low potassium, sodium, and magnesium)
- Dizziness
- Lightheadedness
- Low blood pressure Some patients may experience headache, blurred vision, ringing in the ears, muscle cramps, weakness, or increased thirst.
Serious Side Effects
More serious but less common side effects include severe skin reactions, hearing loss (especially with high intravenous doses), pancreatitis, liver problems, and allergic reactions.
Monitoring and Precautions
Blood sugar levels may be affected, which is important for diabetic patients to monitor. Lasix works by blocking sodium and chloride reabsorption in the kidneys, causing increased water elimination through urine. This diuretic effect helps reduce fluid retention but can lead to dehydration and electrolyte disturbances if not properly monitored. Patients taking Lasix should stay well-hydrated unless otherwise directed by their doctor, have regular blood tests to check electrolyte levels, and report any unusual symptoms promptly. Elderly patients may be more sensitive to these side effects and require closer monitoring, as suggested by a study published in 2018 1.
Dosage and Administration
The starting dose of furosemide is 20–40 mg/day, with a maximum dose of 160 mg/day, as recommended in a study published in 2018 1.
Combination Therapy
Furosemide can be used as a combination therapy with aldosterone antagonist, sequentially or initially, as reported in a study published in 2021 1.
Patient Education
Patients should be educated on the potential side effects of Lasix and the importance of regular monitoring and follow-up appointments, as emphasized in a study published in 2009 1.
From the FDA Drug Label
ADVERSE REACTIONS Adverse reactions are categorized below by organ system and listed by decreasing severity Gastrointestinal System Reactions hepatic encephalopathy in patients with hepato-cellular insufficiency pancreatitis jaundice (intrahepatic cholestatic jaundice) increased liver enzymes anorexia oral and gastric irritation cramping diarrhea constipation nausea vomiting Systemic Hypersensitivity Reactions Severe anaphylactic or anaphylactoid reactions (e. g with shock) systemic vasculitis interstitial nephritis necrotizing angiitis Central Nervous System Reactions tinnitus and hearing loss paresthesias vertigo dizziness headache blurred vision xanthopsia Hematologic Reactions aplastic anemia thrombocytopenia agranulocytosis hemolytic anemia leukopenia anemia eosinophilia Dermatologic-Hypersensitivity Reactions toxic epidermal necrolysis Stevens-Johnson Syndrome erythema multiforme drug rash with eosinophilia and systemic symptoms acute generalized exanthematous pustulosis exfoliative dermatitis bullous pemphigoid purpura photosensitivity rash pruritis urticaria Cardiovascular Reaction Orthostatic hypotension may occur and be aggravated by alcohol, barbiturates or narcotics Increase in cholesterol and triglyceride serum levels Other Reactions hyperglycemia glycosuria hyperuricemia muscle spasm weakness restlessness urinary bladder spasm thrombophlebitis fever
The side effects of Lasix (furosemide) include:
- Gastrointestinal reactions: hepatic encephalopathy, pancreatitis, jaundice, increased liver enzymes, anorexia, oral and gastric irritation, cramping, diarrhea, constipation, nausea, vomiting
- Systemic hypersensitivity reactions: severe anaphylactic or anaphylactoid reactions, systemic vasculitis, interstitial nephritis, necrotizing angiitis
- Central nervous system reactions: tinnitus and hearing loss, paresthesias, vertigo, dizziness, headache, blurred vision, xanthopsia
- Hematologic reactions: aplastic anemia, thrombocytopenia, agranulocytosis, hemolytic anemia, leukopenia, anemia, eosinophilia
- Dermatologic-hypersensitivity reactions: toxic epidermal necrolysis, Stevens-Johnson Syndrome, erythema multiforme, drug rash with eosinophilia and systemic symptoms, acute generalized exanthematous pustulosis, exfoliative dermatitis, bullous pemphigoid, purpura, photosensitivity, rash, pruritis, urticaria
- Cardiovascular reactions: orthostatic hypotension, increase in cholesterol and triglyceride serum levels
- Other reactions: hyperglycemia, glycosuria, hyperuricemia, muscle spasm, weakness, restlessness, urinary bladder spasm, thrombophlebitis, fever 2
From the Research
Lasix Side Effects
The side effects of Lasix (furosemide) have been studied in various clinical settings. Some of the common side effects include:
- Dehydration and hypotension 3
- Hypochloremia, hypokalemia, and hyponatremia 3
- Hyperkalemia, especially when administered with potassium supplements or spironolactone 3
- Bollous dermatosis on the limbs after exposure to sunlight 4
- Decreases in plasma potassium, chloride, and calcium concentrations 5
- Increases in total plasma protein content and urine volume 5
Clinical Consequences
The clinical consequences of furosemide administration can be significant. For example:
- Furosemide-induced hypokalemia, hypochloremia, and hyponatremia can occur in a significant proportion of patients 3
- The use of high doses of furosemide can lead to a gradual decrease in response with time due to progression of renal disease 4
- Furosemide can cause fluid and electrolyte imbalances, which can be particularly problematic in patients with acute kidney injury 6
Special Considerations
In certain populations, such as horses, furosemide can cause significant alterations in electrolyte and acid-base balance 5. Additionally, in patients on hemodialysis, high-dose furosemide can be effective in increasing diuresis and electrolyte excretion, but may not be without side effects 4.