What is furosemide (Lasix) used for?

Furosemide is used to treat high blood pressure or hypertension. It also treats edema (excess fluid in the tissues) caused by kidney disease, liver disease, or congestive heart failure. 

There may be other uses of furosemide — your doctor or pharmacist can give you further drug information.

How does furosemide (Lasix) work?

Furosemide makes the kidneys remove more salt and water from the body through the urine, which helps to lower blood pressure and reduce swelling or fluid retention.  

What is the dosage of furosemide (Lasix)?

Furosemide comes in tablets (20 mg, 40 mg, and 80 mg) and an oral solution (10 mg/mL). It is also available as a vial (injection solution) for intravenous administration. 

For edema: Doctors use the minimum furosemide dosage to obtain a maximal therapeutic response.  In adults, the usual initial dose of furosemide is 20 mg to 80 mg as a single dose. This usually leads to prompt diuresis (urine production). The dose may be increased by 20 mg or 40 mg, or the same dose may be given again 6-8 hours later if needed. An additional dose of furosemide is not given sooner than 6-8 hours after a previous dose. 

For maintenance treatment, the minimum effective dose is given once or twice daily. Patients with severe edema may receive up to 600 mg/day of furosemide. However, doses over 80 mg/day for prolonged periods require careful observation and monitoring. 

In geriatric patients (older adults), the dose of furosemide is usually at the lower end of the dosing range. 

In children, the usual initial dose of oral furosemide is 2 mg/kg of body weight given as a single dose. If the response is not satisfactory, the dose can be repeated but no sooner than 6-8 hours from the previous dose. The dosage may be increased by 1-2 mg/kg. The maximum dose of furosemide in children is 6 mg/kg of body weight. 

For high blood pressure: The usual dose of furosemide for hypertension is 80 mg, typically given as 40 mg twice a day. The dose is adjusted based on response. Your doctor may add other antihypertensive agents if your response to furosemide is not satisfactory. It is important to monitor blood pressure carefully, especially during initial treatment with furosemide and when used with other blood pressure medications. The dosage of other antihypertensive medicines needs to be reduced if furosemide is added to the treatment regimen to prevent an excessive drop in blood pressure. 

Furosemide should be used with caution in older adults, starting at the lower end of the dosing range.