BMA Concise Guide to Medicine & Drugs

Furosemide (Frusemide)

Brand names Froop, Frusol, Lasix, and others

Used in the following combined preparations Co-Amilofruse, Frumil, Lasilactone, and others


Drug group Loop diuretic and antihypertensive drug

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic Yes


Furosemide is a powerful, short-acting loop diuretic that has been in use for over 20 years. Like other diuretics, it is used to treat oedema (accumulation of fluid in tissue spaces) caused by heart failure, and certain lung, liver, and kidney disorders.

Because it is fast acting, furosemide is often used in emergencies to relieve pulmonary oedema (fluid in the lungs). Furosemide is particularly useful for people who have impaired kidney function because they do not respond well to thiazide diuretics.

Furosemide increases potassium loss, which can produce a wide variety of symptoms. For this reason, potassium supplements or a potassium-sparing diuretic may be given with the drug.


Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, liquid, injection.

Frequency and timing of doses Once daily, usually in the morning; 4–6 x hourly (high dose therapy).

Adult dosage range 20–80mg daily. Dose may be increased to a maximum of 2g daily if kidney function is impaired.

Onset of effect Within 1 hour (by mouth); within 5 minutes (by injection).

Duration of action Up to 6 hours.

Diet advice Use of this drug may reduce potassium in the body. Eat plenty of potassium-rich fresh fruits and vegetables, such as bananas and tomatoes.

Storage Keep in original container at room temperature out of the reach of children. Protect from light.

Missed dose No cause for concern, but take as soon as you remember. However, if it is late in the day do not take the missed dose, or you may need to get up during the night to pass urine. Take the next scheduled dose as usual.

Stopping the drug Do not stop the drug without consulting your doctor; symptoms may recur.

Exceeding the dose An occasional unintentional extra dose is unlikely to be a cause for concern. But if you notice any unusual symptoms, or if a large overdose has been taken, notify your doctor.


Adverse effects of furosemide are caused mainly by the rapid fluid loss produced by the drug and the resulting disturbance in body salts and water balance. These effects, which include dizziness, nausea, lethargy, and muscle cramps, tend to diminish as the body adjusts to the drug, although in some cases long-term treatment may lead to depletion of body salts (see Prolonged use). If a rash, photosensitivity, or vomiting occur, you should stop taking the drug and contact your doctor.


Non-steroidal anti-inflammatory drugs (NSAIDs) Some of these drugs may reduce the diuretic effect of furosemide.

Lithium Furosemide may increase blood levels of lithium, leading to an increased risk of lithium poisoning.

Digoxin Loss of potassium may lead to digoxin toxicity when furosemide is taken with this drug.

Aminoglycoside antibiotics The risk of hearing and kidney problems may be increased when these drugs are taken with furosemide.

Thiazides Extremely large amounts of urine may be produced when these drugs are taken with furosemide.


Be sure to tell your doctor if:

· You have long-term liver or kidney problems.

· You have gout.

· You have previously had an allergic reaction to furosemide or sulphonamides.

· You have prostate problems.

· You are taking other medicines.

Pregnancy Safety in pregnancy not established. Discuss with your doctor.

Breast-feeding The drug may reduce milk supply, but the amount in the milk is unlikely to affect the baby. Discuss with your doctor.

Infants and children Reduced dose necessary.

Over 60 Reduced dose may be necessary.

Driving and hazardous work Avoid such activities until you have learned how furosemide affects you because the drug may reduce mental alertness and cause dizziness.

Alcohol Keep consumption low. Furosemide increases the likelihood of dehydration and hangovers after drinking alcohol, and alcohol can increase the blood-pressure-lowering effect of furosemide.


Serious problems are unlikely, but levels of salts, such as potassium, sodium, and calcium, may become depleted. Low blood pressure, palpitations, headaches, problems passing urine, or muscle cramps may develop, particularly in the elderly.

Monitoring Periodic tests may be performed to check kidney function and levels of body salts.