Anticoagulants are medicines that prevent blood clots from forming and existing clots from growing bigger.
Blood clots are a clump of blood that can be useful for stopping bleeding wounds. Unfortunately, they can also block areas like blood vessels. As blood vessels are used to transport blood to the body, if they are blocked, blood won’t be able to reach places such as the heart or the brain. Learn more about blood clots.
Anticoagulants are often referred to as a ‘blood thinner’ but they actually work by interrupting the clot forming process and increasing the time it takes for blood clots to form. This helps prevent blood clots from forming and stops existing clots from growing bigger.
When are anticoagulants used?
Anticoagulants have a variety of uses, including:
In people who are at risk of stroke. A stroke happens when blood clots form in the heart and travel to the brain (usually due to an irregular heart rhythm known as atrial fibrillation).
Oral anticogulants are tablets or capsules that prevent blood clots from forming and existing clots from growing bigger. There are three funded oral anticoagulants in New Zealand – warfarin, dabigatran and rivaroxaban.
These medicines all work well at reducing the risk of blood clots, but they are slightly different. Oral anticoagulant treatment may be needed as a treatment for your condition. Your doctor will discuss the best oral anticoagulant for you. The following are some of the key points to consider.
Are there certain medical conditions when one is preferred?
Yes, sometimes there are. This will be something you should discuss with your doctor in more detail.
How long will I need to take the medicine?
The length of time you need to keep taking your medicine for depends on why it's been prescribed. In many cases, treatment will be lifelong.
How often do I take the medicine?
Warfarin: You will take 1 or more tablets once a day, usually in the evening. The dose will be adjusted depending on blood test results (see below) and you will be given written instructions about how many tablets to take each day.
Dabigatran: You will take 1 dabigatran capsule twice a day.
Rivaroxaban: You will take 1 rivaroxaban tablet once a day.
Will I need regular blood tests?
Warfarin: For the first few weeks and months, you will need frequent blood tests so your doctor can work out the safest dose. After that, most people need to have blood tests every 1–2 months. Some people will need blood tests more or less often than this, and some people are able to test their blood themselves or at a community pharmacy.
Dabigatran: When you first start taking dabigatran, you will need blood tests to check how well your kidneys and liver are working. No regular blood testing to check the level of dabigatran is needed, but you may need to have occasional tests to check your kidneys and liver.
Rivaroxaban: When you first start taking rivaroxaban, you will need blood tests to check how well your kidneys and liver are working. No regular blood testing to check the level of rivaroxaban is needed but you may need to have occasional tests to check your kidneys and liver.
Can my medicines be put into a blister pack?
Warfarin: No, warfarin tablets cannot be put in a blister pack because your daily dose may not be same.
Dabigatran: Dabigatran capsules must be kept in the original foil package to protect them from moisture. If you store the capsules in a pill box or medication reminder box, keep them in the foil packaging. Only remove them from the foil packaging when you are ready to take them.
Rivaroxaban: Yes, they can be placed in a blister pack.
Will I have to change what I eat or drink?
Warfarin: This medicine interacts with many common foods and drinks including alcohol. See warfarin and diet for a list of these. Major changes in what you eat may affect how your body responds to warfarin. Avoid making any major changes to your diet without talking to your doctor or pharmacist first.
Dabigatran: There are no known food interactions, but it is best not to drink too much alcohol.
Rivaroxaban: There are no known food interactions, but it is best not to drink too much alcohol.
Will the medicine interact with other medicines I take?
All anticoagulants interact with many other medicines such as ibuprofen, diclofenac, aspirin and herbal supplements such as garlic, ginkgo, ginseng and St Johns Wort. This can mean your medicines won’t work the way they are meant to, or you may have more side effects. Check with your doctor or pharmacist before starting an anticoagulant or before starting any new medicines, including herbal medicines, vitamins and medicines that you buy yourself, such as pain relief medicine.
What is I have problems swallowing tablets or capsules?
Warfarin: If you are unable to swallow the tablets whole the tablet/s can be crushed.
Dabigatran: Capsules must be swallowed whole and must never be crushed or broken as this can cause serious adverse effects.
Rivaroxaban: If you are unable to swallow the tablets whole the tablet/s can be crushed.
What about the risk of bleeding?
Taking anticoagulants means that blood takes longer to form clots, and this can increase your risk of bleeding. The benefits of using anticoagulants usually outweigh the risks of bleeding. All anticoagulants have a risk of bleeding and this should be something you discuss with your doctor. Your doctor will consider the risk of bleeding for you by considering a number of factors such as:
your age (risk increases as you get older)
hypertension (high blood pressure) that is not controlled with medication
previous myocardial infarction, ischaemic heart disease or cerebrovascular disease
a history of bleeding
the use of other medicines that increase bleeding risk, such as aspirin or other antiplatelet medicines and non-steroidal anti-inflammatory drugs (NSAIDs).
Are the medicines safe in pregnancy and breastfeeding?
Most anticoagulant medicines aren't suitable for pregnant women. Speak to your GP or anticoagulant clinic if you become pregnant or are planning to try for a baby while taking anticoagulants.
What happens if I need non-urgent surgery, including dental surgery?
It is important to tell anyone treating you, including your dentist, physiotherapist or surgeon, that you are taking an anticoagulant. You should tell them at least a few weeks before your appointment. You may not need to stop taking your medicine, but you might need to have a blood test before the procedure to make sure your blood clots at the right speed. Only stop taking your medicine on the advice of your GP or another healthcare professional.
What happens if the effects of the medicine need to be reversed in an emergency (for example, after an injury or before emergency surgery)?
If you have a serious injury or need urgent surgery, you are more likely to have major bleeding because you take an anticoagulant.
Warfarin: A reversal agent is available.
Dabigatran: A reversal agent is available.
Rivaroxaban: There is currently no reversal agent for rivaroxaban available in New Zealand.
To find out more about the risks and benefits of these medicines, talk with your GP or specialist.