Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD

GENERIC NAME: furosemide

BRAND NAME: Lasix

DRUG CLASS AND MECHANISM: Furosemide is a potent diuretic (water pill) that is used to eliminate water and salt from the body. In the kidneys, salt (composed of sodium and chloride), water, and other small molecules normally are filtered out of the blood and into the tubules of the kidney. The filtered fluid ultimately becomes urine. Most of the sodium, chloride and water that is filtered out of the blood is reabsorbed into the blood before the filtered fluid becomes urine and is eliminated from the body. Furosemide works by blocking the absorption of sodium, chloride, and water from the filtered fluid in the kidney tubules, causing a profound increase in the output of urine (diuresis). The onset of action after oral administration is within one hour, and the diuresis lasts about 6-8 hours. The onset of action after injection is five minutes and the duration of diuresis is two hours. The diuretic effect of furosemide can cause depletion of sodium, chloride, body water and other minerals. Therefore, careful medical supervision is necessary during treatment. The FDA approved furosemide in July 1982.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS: Tablets: 20, 40, and 80mg. Oral solution: 10 mg/ml, 40 mg/5 ml. Injection: 10 mg/ml

STORAGE: Furosemide should be stored at room temperature in a light resistant container.

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

DOSING: The usual starting oral dose for treatment of edema in adults is 20-80 mg as a single dose. The same dose or an increased dose may be administered 6-8 hours later. Doses may be increased 20-40 mg every 6-8 hours until the desired effect occurs. The effective dose may be administered once or twice daily. Some patients may require 600 mg daily. The starting oral dose for children is 2 mg/kg. The starting dose may be increased by 1-2 mg/kg every 6 hours until the desired effect is achieved. Doses greater than 6 mg/kg are not recommended. The recommended dose for treating hypertension is 40 mg twice daily.

DRUG INTERACTIONS: Administration of furosemide with aminoglycoside antibiotics (for example, gentamicin) or [ethacrynic acid (Edecrin) - another diuretic] may cause hearing damage. Furosemide competes with aspirin for elimination in the urine by the kidneys. Concomitant use of furosemide and aspirin may, therefore, lead to high blood levels of aspirin and aspirin toxicity. Furosemide also may reduce excretion of lithium (Eskalith, Lithobid) by the kidneys, causing increased blood levels of lithium and possible side effects from lithium. Sucralfate (Carafate) reduces the action of furosemide by binding furosemide in the intestine and preventing its absorption into the body. Ingestion of furosemide and sucralfate should be separated by two hours.

PREGNANCY: There are no adequate studies of furosemide in pregnant women.

NURSING MOTHERS: Furosemide is secreted in breast milk. Nursing mothers should avoid breastfeeding while taking furosemide.

SIDE EFFECTS: Common side effects of furosemide include low blood pressure, dehydration and electrolyte depletion (for example, sodium, potassium). Less common side effects include jaundice, ringing in the ears (tinnitus), sensitivity to light (photophobia), rash, pancreatitis, nausea, diarrhea, abdominal pain, and dizziness. Increased blood sugar and uric acid levels also may occur.

Reference: FDA Prescribing Information