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Warfarin - ein Antikoagulans

Warfarin is an anticoagulant. It will be prescribed if you have an unwanted clot in your blood, or if you are at risk of having an unwanted clot.

You may be given a yellow anticoagulant treatment booklet; read this carefully and carry it with you at all times.

You will need to have regular blood tests to measure how quickly your blood clots.

What you eat and drink can affect your treatment. Do not change your diet without discussing it with your doctor first; do not drink cranberry juice; and only drink moderate amounts of alcohol.

Auf einen Blick

  • Warfarin is an anticoagulant medicine that helps prevent harmful blood clots.

  • It works by reducing the effects of vitamin K, which is involved in blood-clotting.

  • You will need regular blood tests to check how quickly your blood clots.

  • Your dose of warfarin may be adjusted based on these blood test results.

  • Always carry your yellow anticoagulant treatment booklet with you.

  • Avoid some foods, drinks, and medicines that can affect warfarin's action.

  • Unusual bleeding or bruising needs immediate medical attention.

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About warfarin

Art des Medikaments

Anticoagulant

Verwendet für

Prevention and treatment of harmful blood clots

Verfügbar als

Tabletten und flüssige orale Medizin

Warfarin is an anticoagulant, which means that it increases the time it takes for your blood to clot. It works by reducing the effects of vitamin K, which is a vitamin your body uses in the process of blood-clotting.

Warfarin is used to prevent unwanted clots from forming if you have a condition that puts you at risk of this happening, such as Vorhofflimmern. It is also used to prevent any clots that may have already formed in the blood vessels of your legs, lungs or heart from becoming larger and causing problems.

Warfarin is currently the most prescribed anticoagulant although newer anticoagulants are increasingly being prescribed.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking warfarin it is important that your doctor knows:

  • Wenn Sie schwanger sind, versuchen, schwanger zu werden oder stillen.

  • If you have any cuts or wounds.

  • If you have a condition that increases your risk of bleeding, such as a stomach ulcer, or if you have had surgery recently, or if you have recently had a stroke.

  • Wenn Sie Probleme mit der Funktionsweise Ihrer Leber oder Ihrer Nieren haben.

  • Wenn Sie hohen Blutdruck (Hypertonie) haben.

  • If you have been told you have an infection of your heart, called bacterial endocarditis.

  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines. It is particularly important that you tell your doctor if you are also using an anti-fungal preparation containing miconazole, as this medicine can affect the way warfarin works. Miconazole is an ingredient in creams, ointments, sprays, and powders used for fungal skin infections such as athlete's foot, and also in gels and creams for thrush.

  • Wenn Sie jemals eine allergische Reaktion auf ein Medikament hatten.

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  • Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack of tablets and any additional information you have been given by your doctor. These will give you more information about warfarin and will provide you with a full list of the side-effects which you may experience from taking it.

  • Take warfarin exactly as you have been advised by your doctor or anticoagulant clinic. You should aim to take warfarin at the same time each day. This will help keep the levels of warfarin in your blood steady, and will also help you to avoid missing any doses. It is usually recommended that you take warfarin at six o'clock in the evening.

  • Warfarin tablets are available in different strengths. Your dose may be made up of more than one strength of tablet. Each strength of tablet is a different colour to help you tell the difference between them; 0.5 mg tablets are white, 1 mg tablets are brown, 3 mg tablets are blue and 5 mg tablets are pink.

  • If you have been prescribed the oral liquid medicine you will need to take 1 ml for every 1 mg of your dose - for example, a 3 mg dose is 3 ml of liquid. Use an oral syringe to measure your dose carefully.

  • If you forget to take a dose, take it as soon as you remember. If you do not remember until the following day, skip the missed dose. Do not take two doses together to make up for a forgotten dose, and remember to let your doctor know about any missed doses when you next have your blood test.

  • Continue to take warfarin tablets regularly until your doctor tells you to stop. A course of treatment typically lasts from six weeks to three months, although some people may be advised to continue taking warfarin for longer than this.

  • You will be given a yellow anticoagulant treatment booklet; read this carefully as it gives you information about when you should contact a doctor for advice. Carry it with you at all times in case of an emergency and a doctor needing to know that you are on warfarin, and at what dose.

  • You will need regular blood tests to check on how quickly your blood clots when you are taking warfarin. Blood tests may be needed quite often at first, but should reduce in frequency quite quickly. The extent to which warfarin is working is measured by the International Normalised Ratio (INR), which is a measure of the ability of your blood to prevent clotting. The amount of warfarin that you need to take will depend upon the result of these blood tests, and this is why your dose may change from time to time. The aim is to get the dose of warfarin just right so your blood does not clot as easily as normal, but not so much as to cause bleeding problems.

  • Changing your diet suddenly can affect your INR, especially if you begin to eat more vegetables and salad. You should not begin a weight-reducing diet without discussing it with your doctor first. A major change in diet may mean that you need closer monitoring and may need a change in warfarin dose.

  • Only drink alcohol in small amounts, as this can affect the levels of warfarin in your body. Limit the amount of alcohol that you drink to a maximum of one or two units in any day, and never binge drink.

  • Drinking cranberry juice can interfere with warfarin and affect your INR, so it is best if you avoid cranberry juice altogether.

  • If you buy any medicines, check with a pharmacist that they are safe to take with warfarin. For example, you should not take some painkillers (such as aspirin and other anti-inflammatory painkillers) and some vitamin and herbal preparations while you are on warfarin. If you need to take a painkiller, you may take paracetamol, but you should let your doctor know if you need to take it regularly.

  • Because warfarin is used to prevent blood clots from forming, you should try to avoid activities that could cause you to cut or bruise yourself, such as contact sports. Let your doctor know if you have any falls or injuries.

  • You should avoid getting pregnant while you are taking warfarin. Make sure you have discussed with your doctor which types of contraception are suitable for you and your partner.

  • If you are due to have any injections, or any medical or dental treatment, tell the person carrying out the treatment that you are taking warfarin, and show them your anticoagulant booklet. It is important that they know you may take longer to stop bleeding. If you are due to have surgery, you may be advised by the clinic to stop taking warfarin for a few days beforehand.

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Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the more common ones associated with warfarin - the most common are bleeding and bruising. You will find a full list in the manufacturer's information leaflet supplied with your medicine. Speak with your doctor or pharmacist if any of the following continue or become troublesome.

Warfarin side-effects

Was kann ich tun, wenn ich das erlebe?

Unusual bleeding or bruising, blood in your urine or stools (faeces)

See your doctor straightaway - your dose of warfarin will probably need to be reduced

Durchfall

Trinken Sie viel Wasser, um verlorene Flüssigkeiten zu ersetzen

Skin rash, painful or 'purple' toes

Speak with your doctor about this

Haarausfall

Wenn dies problematisch wird, sprechen Sie mit Ihrem Arzt

Sich krank fühlen (Übelkeit) oder krank sein (Erbrechen)

Stick to simple meals until this passes

Painful or tender abdomen, yellowing of your skin or the whites of your eyes (jaundice)

Speak with your doctor about this straightaway

Wenn Sie andere Symptome bemerken, die Ihrer Meinung nach auf die Tabletten zurückzuführen sein könnten, sprechen Sie mit Ihrem Arzt oder Apotheker für weitere Ratschläge.

  • Bewahren Sie alle Medikamente außerhalb der Reichweite und Sicht von Kindern auf.

  • An einem kühlen, trockenen Ort aufbewahren, fern von direkter Hitze und Licht.

  • The oral liquid medicine lasts for 28 days after first opening, after that time you will need a fresh supply. It is a good idea to write on the label the date you opened the bottle.

Wichtige Informationen über alle Medikamente

Nehmen Sie niemals mehr als die vorgeschriebene Dosis ein. Wenn Sie vermuten, dass Sie oder jemand anderes eine Überdosis dieses Medikaments eingenommen haben könnte, gehen Sie in die Notaufnahme Ihres örtlichen Krankenhauses. Nehmen Sie den Behälter mit, auch wenn er leer ist.

Dieses Medikament ist für Sie. Geben Sie es niemals an andere Personen weiter, auch wenn deren Zustand ähnlich erscheint wie Ihrer.

Bewahren Sie keine abgelaufenen oder unerwünschten Medikamente auf. Bringen Sie sie zu Ihrer örtlichen Apotheke, die sie für Sie entsorgt.

Wenn Sie Fragen zu diesem Medikament haben, fragen Sie Ihren Apotheker.

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Häufig gestellte Fragen

What is the main purpose of taking warfarin?

Warfarin is an anticoagulant medicine, which means it helps to prevent harmful blood clots from forming in your body. It's used if you have a condition that puts you at risk of clots, like atrial fibrillation, or to stop existing clots in your legs, lungs, or heart from getting bigger and causing further problems.

How does warfarin actually work inside my body?

Warfarin works by reducing the effects of vitamin K. Vitamin K is a key vitamin that your body uses in the process of making blood clot. By reducing its effects, warfarin increases the time it takes for your blood to clot.

Why is it important for my doctor to know about all my other medications, including herbal ones, before I start warfarin?

It's crucial for your doctor to know about all your medicines because some drugs can interact with warfarin and affect how it works. This includes over-the-counter, herbal, and complementary medicines. For example, some anti-fungal treatments containing miconazole can affect warfarin, and certain painkillers like aspirin or some vitamin preparations should be avoided while on warfarin.

What should I do if I accidentally miss a dose of warfarin?

If you forget to take a dose, take it as soon as you remember. However, if you don't remember until the following day, you should skip the missed dose. Never take two doses at once to make up for a forgotten one. It's also important to let your doctor know about any missed doses at your next blood test appointment.

Why do I need to carry a yellow anticoagulant treatment booklet, and what should I do with it?

You will be given a yellow anticoagulant treatment booklet that contains important information about your warfarin treatment. You should read it carefully and carry it with you at all times. This is vital in case of an emergency, as it informs medical staff that you are taking warfarin and at what dose, which can be crucial for your care.

Are there any specific foods or drinks I should avoid while taking warfarin?

Yes, it's advised to avoid cranberry juice altogether, as it can interfere with warfarin and affect how well it works. Also, sudden major changes in your diet, particularly if you start eating a lot more vegetables and salads, can affect your INR (how quickly your blood clots), so discuss any major dietary changes or weight-reducing diets with your doctor first. Alcohol should only be consumed in small amounts, typically no more than one or two units a day, and binge drinking must be avoided.

What should I do if I notice unusual bleeding or bruising, or see blood in my urine or stools?

If you experience unusual bleeding or bruising, or notice blood in your urine or stools, you should see your doctor straight away. These can be signs that your warfarin dose might be too high, and it will probably need to be reduced.

Weiterführende Literatur und Referenzen

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Über den AutorVollständige Biografie anzeigen

Autorenbild

Michael Stewart, MRPharmS

Manager für die Überprüfung von Beipackzetteln – Auftragnehmer, Apotheker

BPharm (Hons), MRPharmS

Michael ist ein Gemeindapotheker, der in den Midlands und South Yorkshire praktiziert und über mehr als 20 Jahre Erfahrung in der Beratung zu Medikamenten und medizinischen Bedingungen verfügt. Er hat einen starken Hintergrund in der Gesundheitsausbildung, da er Schulungskurse für Apothekenteams und Mitarbeiter von Pflegeeinrichtungen, einschließlich Krankenschwestern, erstellt und durchgeführt hat. Er hat auch zu Apothekenbeiräten für das Management von geringfügigen Erkrankungen in der Gemeinschaft beigetragen.

Über den Rezensenten

Autorenbild

Sid Dajani

Sultan Dajani qualifizierte sich 1994 an der London School of Pharmacy und wurde das jüngste gewählte Mitglied des Rates der Royal Pharmaceutical Society seit ihrer Gründung im Jahr 1842.

Artikelverlauf

Die Informationen auf dieser Seite wurden von qualifizierten Klinikern verfasst und begutachtet.

  • Nächste Überprüfung fällig: 13. Aug 2026
  • 14. Aug 2023 | Neueste Version

    Zuletzt aktualisiert von

    Michael Stewart, MRPharmS

    Begutachtet von

    Sid Dajani
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