Warfarin

About warfarin

Warfarin works by thinning the blood.

Before taking warfarin

Before taking warfarin make sure your doctor or pharmacist knows:

• If you are pregnant, trying for a baby or breast-feeding.
• If you suffer from a blood disorder.
• If you have a peptic ulcer.
• If you have any severe wounds at present.
• If you suffer from high blood pressure.
• If you have had recent surgery, or are due for surgery in the near future.
• If you suffer from problems with your thyroid.
• If you suffer from liver or kidney problems.
• If you consume a lot of cranberry juice.
• If you have been diagnosed as having an infection of the heart.

How to take warfarin

• Follow the instructions given to you by your doctor.
• Your dose should be taken at the same time each day.

Getting the most from your treatment

• You should be given an anticoagulant record book; read this, and always carry it with you.
• Warfarin tablets are available in different strengths. Your dose may be made up of more than one strength tablet. Each strength tablet is a different colour to help you tell the difference between them; 0.5mg tablets are white, 1mg tablets are brown, 3mg tablets are blue and 5mg tablets are pink.
• You will have regular blood tests to check how the warfarin in your blood is working- these blood tests are very important. The extent to which warfarin is working is measured by the INR (International Normalised ratio), a measure of the ability of your blood to prevent clotting.
• Changing your diet suddenly can affect your warfarin levels, especially if you begin to eat more vegetables and salad or if you change the amount of fatty foods you have been eating. You should not begin a weight reducing diet without discussing it with your doctor first.
• Avoid drinking cranberry juice while you are taking this medicine as it may affect the levels of warfarin in your body.
• Alcohol should only be drunk in moderation. Alcohol can also affect the levels of warfarin in your body.
• Do not take any 'over the counter medicines', herbal remedies or vitamin preparations without discussing this with your doctor first, as these may affect your warfarin levels.

Can warfarin cause problems

Along with their useful effects all medicines can cause unwanted side effects, which usually improve as your body adjusts to the new medicine. Speak with your doctor or pharmacist if any of the following side effects continue or become troublesome.

How to store warfarin

• Keep all medicines out of the reach of children.
• Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

References

• British National Formulary; 54th Edition (September 2007) British Medical Association and Royal Pharmaceutical Society of Great Britain, London.
• Martindale: The Complete Drug Reference