Dear Wwynn,
Here is some information that should help you.
What does warfarin do and how effective is it?
Warfarin interferes with certain chemicals in the blood to prevent blood clots forming so easily. This is known as anticoagulation. Some people call anticoagulation 'thinning the blood' although the blood is not actually made any thinner. Warfarin is the most commonly used anticoagulant drug. Recent studies which looked at people with AF have shown that by taking warfarin the risk of having a stroke is greatly reduced.
Overall, warfarin reduces the risk of stroke by nearly two-thirds. In other words, warfarin treatment can prevent about 6 in 10 strokes that would have occured in people with AF. The greatest benefit is seen in those people who are in the 'high risk' category of having a stroke (described above). For example:
- For people with AF who are at high risk of stroke, about 80-90 strokes will be prevented each year for every thousand people treated with warfarin.
- For people with AF who are at moderate risk of stroke, about 25 strokes will be prevented each year for every thousand people treated with warfarin.
Are there any risks with taking warfarin?
As with most treatments, there is some risk if you take warfarin. The main risk is that a bleeding problem may develop as the blood will not clot so well. For every thousand people with AF who take warfarin, about nine people per year are likely to have a serious bleeding problem from the treatment. For example, you could develop a bleeding ulcer in your intestines (guts), or suffer a bleed into the brain (a cerebral haemorrhage). If you have a serious bleed you are likely to need to be admitted to hospital, often needing a blood transfusion, and it can even result in death.
Most people with AF who have a high or medium risk of having a stroke are advised to take warfarin. However, some people with a moderate risk may be treated with aspirin rather than warfarin (see below), particularly if the risks of taking warfarin are higher than average. People with a low risk of having a stroke are not usually advised to take warfarin. This is because the benefit does not usually outweigh the risk of serious bleeding problems with taking warfarin. In short, the decision to take warfarin is a joint decision between you and your doctor. It involves weighing up the risk of having a stroke against the small risk of a complication from taking warfarin.
Aspirin is another drug that helps to prevent blood clots forming. It is not as effective as warfarin, but is less likely to cause serious problems. It is usually advised if you only have a low risk of stroke, or if you cannot take warfarin or do not wish to take warfarin.
What does warfarin treatment involve?
Most people who take warfarin attend a 'warfarin clinic'. This may be at your GP practice, or at the local hospital. The clinic is run by a health professional specially trained in anticoagulation. He or she may be a doctor, specialist nurse, trained pharmacist, etc.
You will need regular blood tests to check on how quickly your blood clots when you are taking warfarin. Blood tests (and clinic visits) may be needed quite often at first, but should reduce in frequency quite quickly. 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.
You will be advised on how to take warfarin, and if it affects any other medication that you take. For example, the following are commonly advised:
- You should aim to take warfarin at the same time each day.
- If you accidentally miss a dose, NEVER take a double dose 'to catch up' (unless specifically advised by a doctor or by the person who runs the warfarin clinic).
- Seek advice promptly if you think that you have taken too much warfarin by mistake, or have missed any doses.
