A quick look at the facts
- Bioactive ingredient
- Furosemide (also spelled frusemide in older UK sources)
- Drug class
- Loop diuretic
- Typical strengths in the UK
- Commonly 40 mg and 100 mg tablets; other forms exist for specialist use
- Frequent clinical uses
- Relief of fluid retention from heart, liver or kidney disease, acute pulmonary oedema, and adjunct in some hypertensive situations
- Related topics
- Blood pressure control, diuretic selection, and anti-doping considerations
If you are unfamiliar with this medicine, begin with the Overview page. For safety issues read Safeguards and verify the details Medication Interaction Effects. For information on legal issues jump to Legislative and Regulatory affairs Notices.
Panorama of the crestic: what furosemide does and how the workflow comes together
Furosemide (brand name Lasix) produces a strong diuretic effect by blocking the reabsorption of sodium and chloride in the thick ascending limb of the loop of Henle in the kidney. The result is increased urine output and loss of several electrolytes including sodium, chloride, potassium, calcium and magnesium.
It is widely used to reduce oedema associated with heart failure, liver cirrhosis and renal disease. In emergency care it helps manage acute pulmonary oedema, and in some specialist settings it is used to assist with blood pressure control or cerebral oedema under expert supervision.
To jump straight to unfavorable health effects, go to Possible drug adverse outcomes, or to risk alerts on user two-way communication in action see Drug Interaction Issues.
Instructions for dosage and administration
Always follow the exact instructions given by your prescriber. Take the tablets using water to aid swallowing. Taking doses earlier in the day helps avoid nocturnal urination that can disturb sleep.
- Do not alter or stop your dose without medical advice.
- If your prescriber has put you on a multiple-dose schedule, try to avoid late-evening doses when possible.
- In hospital acute care, furosemide may be administered by injection by qualified staff.
See Dose was not taken for guidance on a forgotten tablet. If you have concerning symptomsreconsideration Overdose and Potential medication undesired reactions.
Important safety measures before treatment and during treatment
Tell your doctor or pharmacist about all medical conditions and medicines you take. Extra caution is needed in the presence of:
- Reduced kidney function or chronic kidney disease
- Hepatic function impairment, including cirrhosis
- Diabetes mellitus, the sugar disease or high uric acid states such as gout
- Autoimmune related conditions such as lupus
- Known allergy to sulfonamide-type medicines
Furosemide increases the chance of dehydration and electrolyte imbalance. Your clinician may recommend blood tests and will advise on fluid intake. The drug can cause dizziness; do not drive or operate machinery until you know how it affects you. Pregnant or breastfeeding patients should only use it after discussion with their clinician.
Conditions under which furosemide should be avoided
Furosemide should be avoided unless a specialist decides otherwise in these situations:
- Hypersensitivity to furosemide or any component of the product
- Anuria or severe acute renal failure with no urine output
- Profound liver dysfunction with hepatic coma or a pre-coma condition
- Marked arterial hypotension or circulatory shock
- Acute pancreatitis or uncontrolled hyperglycaemic coma
- Significant urinary tract obstruction, for example urethral stenosis
- Acute glomerulonephritis syndrome
Potential effects during use
Contact a healthcare professional immediately if you notice signs of an allergic reaction such as rash, wheeze or facial swelling.
Other symptoms that need prompt attention include:
- Acute reduction in urine output or anuria.
- Severe weakness, drowsiness, confusion or dizziness
- Intense thirst, dry mouth, nausea or vomiting
- A quick heartbeat with irregular rhythm, muscle cramps or pain
- Easy bruising, unusual bleeding or signs of infection
- Hearing changes or tinnitus, particularly at high doses or with other ototoxic drugs
- Red or blistering skin rash, photosensitivity reactions, or hair thinning
Because furosemide can cause electrolyte disturbances such as low potassium, sodium or magnesium, your team may do periodic blood tests to monitor levels and adjust treatment.
Drug communication in action guidance to keep in mind
Certain drug combinations increase risks or reduce the effect of medicines. Important examples include:
- Aminoglycoside antibiotics like gentamicin and ethacrynic acid: increased risk of hearing damage
- Lithium: furosemide may reduce renal clearance of lithium and elevate lithium levels
- Digitalis glycoside: low potassium levels caused by diuretics can raise the risk of digoxin toxicity
- NSAIDs and aspirin: nonsteroidal anti-inflammatory drugs can blunt the diuretic effect; salicylates may affect salicylate concentrations
- Sucralfate: it can reduce furosemide absorption; separate dosing by at least two hours
- Other antihypertensives, alcohol or nitrates: additive blood pressure lowering and increased dizziness
Always show your current medication list to any prescriber. If you develop symptoms listed in Possible therapy post use effects, seek urgent advice.
Steps to take for a the dose was missed
If you miss a single tablet:
- Take it when you recall, unless it is near the time for your next scheduled dose.
- If the next dose is due soon, skip the missed tablet and continue as normal.
- Do not take two doses together to compensate for a dose you missed.
Hospital or single-dose administrations follow the schedule set by clinical staff; speak to them if you have concerns.
Overdose syndrome
Seek immediate medical help or call emergency services if someone has taken too much furosemide or shows severe symptoms such as fainting, extreme weakness, confusion, persistent dizziness, severe thirst or hearing problems. In an intentional overdose can lead to severe dehydration, electrolyte imbalances, hypotension and auditory effects.
Storage unit
- This item should be kept away from children, out of reach and sight.
- Store in a cool, dry place at room temperature away from direct light.
- Keep tablets in their original container with the lid closed tightly.
Substitute therapies and comparable drugs
Selection of an the other option depends on the clinical situation, kidney function and treatment goals. Options often considered include:
- Torasemide (torsemide): another loop diuretic with a longer duration in some patients
- Bumetanide: loop diuretic that is more potent on a milligram-to-milligram basis
- Spironolactone or eplerenone: potassium-sparing aldosterone antagonists used in heart failure or cirrhosis-related ascites
- Thiazide diuretics such as bendroflumethiazide or indapamide: used for hypertension or combined with loop diuretics for resistant oedema
- Hydrochlorothiazide: commonly used for blood pressure control; less effective for rapid fluid removal
Discuss tolerability, real time monitoring needs and costs with your clinician or pharmacist. See Prices around the United Kingdom to lay out a rough cost comparison.
Price dynamics in the UK - rough guide in GBP
Prices vary by NHS prescriptions, private supply, brand, and pack size. The figures here are approximate and intended for general orientation only.
- NHS: In England a standard prescription charge applies per item (for 2024 to 2025 it is 9.ninety pounds sterling Prescriptions are free in Scotland, Wales and Northern Ireland for most patients.
- Private prescriptions: small packs of generic furosemide 40 mg (28 tablets) often cost around 1 to 5 GBP for the medicine, plus a pharmacy dispensing fee which may be 5 to 10 GBP.
- Online clinics: combined consultation and dispensing offers may price small generic packs typically between about 9 and 25 GBP excluding delivery.
- Comparative costs: bumetanide generics tend to be in a similar low-price range; torasemide may be slightly more costly but still affordable; spironolactone and thiazides are generally inexpensive generics.
Ask your pharmacist whether a generic substitute or a larger pack will reduce your per-tablet cost.
Information on statutory and regulatory provisionsrmation - United Kingdom
- Prescription status: Furosemide is a Prescription Only Medicine (POM) and is regulated by the Medicines and Healthcare products Regulatory Agency (MHRA). It should not be supplied in the UK without a valid prescription and must be dispensed by a UK-registered pharmacy.
- Import rules: Personal importation of prescription medicines into the UK without a prescription is normally not allowed. Border Force plus the MHRA may detain or seize medicines supplied unlawfully.
- Sporting rules: Diuretics such as furosemide are listed as prohibited by WADA and by UK Anti-Doping (UKAD) because they can be used as masking agents. Athletes require a Therapeutic Use Exemption for legitimate medical use.
- Legal safety: Sharing prescription medicines or using another person’s prescription is unsafe and may be illegal.
- Driving and work: If you experience dizziness or faintness after taking furosemide, avoid driving or operating machinery until these effects resolve.
For more on safe use see Preventive safeguards and Drug Combinations and Communication and also the back and forth between people.
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