Lasix (Furosemide)

Furosemide is a powerful diuretic. Furosemide is used to treat excessive fluid accumulation and swelling (edema) of the body caused by heart failure, cirrhosis, chronic kidney failure, and nephrotic syndrome. It is sometimes used in conjunction with other blood pressure pills to treat high blood pressure.

Furosemide is a potent diuretic (water pill). Furosemide works by blocking the absorption of salt and fluid in the kidney tubules, causing a profound increase in urine output (diuresis). The diuretic effect of furosemide can cause body water and electrolyte depletion. Therefore, careful medical supervision is necessary during treatment.

Patients allergic to sulfa may also be allergic to furosemide because of a similarity in the chemical structure of the medications. Furosemide should be avoided in kidney failure. Even though furosemide is important in treating excess fluid accumulation in patients with cirrhosis, sudden loss of fluid and electrolytes in these patients can worsen kidney function and even cause the patient to go into a coma. Furosemide can cause lowering of blood potassium, sodium, and magnesium levels. Low potassium and magnesium levels can lead to heart rhythm abnormalities, especially in patients already taking digoxin (Lanoxin). Please visit the digoxin (Lanoxin) site for further information.

Blood uric acid levels can increase during furosemide treatment, but precipitation of acute gout is rare. Furosemide may increase the toxic effect of aminoglycoside antibiotics on the ear, especially in patients with kidney dysfunction. Furosemide reduces the kidney excretion of lithium and can lead to lithium toxicity. Furosemide may impair kidney function when administered together with aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs). Periodic blood tests are performed to monitor kidney function and electrolytes during treatment with furosemide.

Commonly observed side effects are low blood pressure, and water and electrolyte depletion. Less common side effects include jaundice, ringing in ears (tinnitus), light sensitivity, rash, pancreatitis, nausea, abdominal pain, dizziness, anemia, and other blood disorders.

• If you experience any of the following serious side effects, stop taking furosemide and seek emergency medical attention or call your doctor immediately:
  • an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives);
  • muscle cramps or weakness;
  • an irregular heartbeat;
  • abdominal pain or diarrhea;
  • low blood pressure (weakness, dizziness, fatigue); or
  • decreased hearing.
• Other, less serious side effects may be more likely to occur. Continue to take furosemide and talk to your doctor if you experience
  • dry mouth or increased thirst;
  • headache, dizziness, or lightheadedness;
  • constipation;
  • increased sensitivity to sunlight;
  • a rash;
  • jaundice (yellow skin or eyes);
  • ringing in the ears;
  • nausea;
  • easy bleeding or bruising; or
  • numbness in the hands or feet.
• Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.