Growing up with Warfarin

The aim of this fact sheet is to provide you with information if your child is on warfarin. 

What is warfarin?
Warfarin is an anticoagulant drug. This means that it increases the time it takes for the blood to clot. Warfarin helps the blood to flow easily and prevents clots from forming. Warfarin comes as a pill to take by mouth.

Why is warfarin prescribed?
Warfarin in prescribed to people who are at risk of developing blood clots. It is also given to anyone who has developed a clot and needs treatment. 

Getting the dose right
It is important that patients get the correct dose of warfarin. Too small a dose could fail to prevent blood clots developing, while too large a dose could prevent the blood clotting for too long and lead to bleeding problems. 

To check that a patient is getting the right dose of warfarin they have to have an INR test. The doctor will set a target INR range and the test result needs to fall within that range. Some children, especially when they first start taking warfarin, need to be tested every day. Once the result becomes more stable then the length of time between tests increases.

What Does INR mean?
The proper name for the blood test done by INR machines is Prothrombin Time (PT) and INR, or International Normalised Ratio, is the globally recommended unit for measuring Prothrombin Time.

What does an INR test involve?
The test involves pricking the patient's finger and putting a small drop of blood onto a testing strip. The INR machine then calculates the length of time it is taking the blood to clot. 

A number of factors can affect the INR result. For example: 

• foods containing lots of vitamin K;
• changes in body weight;
• illness; and
• drinking over 2 units of alcohol a day.

Your doctor or anti-coagulation nurse should explain how you can avoid affecting the result and you can ask them any questions.

Many people on warfarin have to go into their local hospital or surgery to have their INR tests. This can take up a lot of time and result in children missing school etc. The Children's Heart Federation provide INR machines to some children so that they can do their tests at home. For more information go to our website www.chfed.org.uk or phone our free infoline 0808 808 5000. 

Sports and warfarin
Even when the warfarin dose is correct patients are at greater risk of bleeding and bruising. Most people who are taking warfarin are advised not to play contact sports like football, hockey or rugby. Martial arts are also not a good idea. However, there are lots of non-contact sports that people taking warfarin can enjoy such as running, cycling, tennis and golf. 

Telling schools
If a child is taking warfarin, then it is important that their school is told. P.E. teachers will need to know that a child cannot take part in contact sports and the school will also want to know how to care for a child if they start bleeding.