Anticoagulants are a type of medicine designed to “stop blood clots".
They are commonly prescribed to people who are at risk of stroke, where blood clots form in the heart and travel to the brain (usually due to an irregular heart rhythm known as atrial fibrillation).
The are also prescribed to people with artificial heart valves and are used for the prevention and treatment of deep vein thrombosis, where blood clots form in veins deep within the legs and pelvis. From here, the clots can travel to the lungs and cause a pulmonary embolism.
Which anticoagulants are available in New Zealand?
There are many anticoagulants in New Zealand. Some are taken by mouth (orally) as tablets or capsules and some are given by injection.
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Anticoagulants given orally (tablets or capsules)
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Anticoagulants given by injection
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Examples include:
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Examples include:
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Warfarin and dabigatran are most commonly prescribed. Read more about which anticoagulant is best for you.
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These are commonly used in hospital. Some people may be given these to inject at home. If you need to do this, your healthcare professional will show you how.
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What is the risk of bleeding?
Because anticoagulants stop blood clots, they may cause bleeding. Before prescribing, your doctor will consider the risk of bleeding. Some things increase the risk of bleeding, 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
- anaemia
- 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).
What are the signs of bleeding?
One sign is that you may bleed or bruise easily. Also, if you bleed, the bleeding may not stop as quickly as normally.
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Contact your healthcare provider urgently if these things happen to you:
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- Blood in your urine or stools (poos). The blood might be bright red, but if you are bleeding from your stomach, your stools may be a black or plum colour.
- In women, heavy bleeding during a period or other heavy vaginal bleeding.
- Severe bruising.
- Blood in your sick (vomit).
- Coughing up blood.
- If you cut yourself and the bleeding does not stop as quickly as normal.
- Nosebleeds (lasting for longer than 10 minutes).
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When is taking anticoagulants not suitable?
Your doctor will talk to you about the benefits and risks. Anticoagulants are not suitable for people who:
- are pregnant
- have a stomach ulcer
- have had a bleed into the brain (a haemorrhagic stroke)
- are going to have surgery and there is a risk of a major bleed
- have very high blood pressure.
How long do I need to continue anticoagulant treatment?
This will depend on what you are taking it for. Some people only need it for a few weeks, such as after surgery, or for months such as for deep vein thrombosis.
Other people need to take an anticoagulant for the rest of their lives (people with atrial fibrillation or a mechanical heart valve). Your doctor will advise what is best for you.
References
- Dabigatran revisited Best Practice Jnl, Feb 2013
- Dabigatran etexilate New Zealand Formulary v.52 -01 Oct 2016
Deciding between warfarin and dabigatran
Until 2011, the most commonly prescribed anticoagulant in New Zealand was warfarin (known here by the brand names Marevan and Coumadin). Since then, new anticoagulants have become available, such as dabigatran.
Today, both warfarin and dabigatran are commonly used. Both medications work well at thinning the blood and reducing the risk of blood clots. However, warfarin is more suitable for some people and dabigatran for others.
Once it has been decided that anticoagulant treatment is needed, discuss the differences between warfarin and dabigatran (described below) with your doctor. This will help guide the selection of the anticoagulant most suitable for you and your situation.
What is warfarin?
Warfarin affects vitamin K-derived clotting factors. It is effective in reducing blood clots, but:
- It interacts with alcohol and many common foods, vitamins and medications such as antibiotics.
- You need to have regular blood testing to ensure your INR (clotting ratio) is stable and you have the correct dose.
- Your warfarin dose may need to be changed because if you take too much, you are at risk of bleeding. If you don't take enough, you are at risk of stroke (clot in the brain) or pulmonary embolus (clot in the lung).
What is dabigatran?
Dabigatran is a direct thrombin inhibitor, a new class of drug that blocks the activity of thrombin, the enzyme responsible for clotting.
- Dabigatran has been shown to be as effective as warfarin but also has a risk of bleeding.
- There are no known food interactions and only a few drug interactions.
- Dabigatran does not need blood testing and dose changes like warfarin.
- Once the right dose of dabigatran has been decided, you can take the same dose, without regular blood tests.
Who can take dabigatran?
In New Zealand dabigatran can be prescribed:
- for people who have irregular heart rhythm called atrial fibrillation, or
- to prevent blood clots forming in the veins (venous thromboembolism) after surgery such as hip or knee replacements.
What are the side effects of dabigitran?
- About 10 per cent (10 in every 100) of people taking dabigatran have bad indigestion, and prefer to take warfarin instead.
- Unusual bleeding can also happen with dabigatran. If this happens see your doctor as soon as possible.
Who should stay on warfarin?
Dabigatran is not recommended for people with:
- mechanical heart valves
- severe valvular heart disease
- long-term treatment for deep vein thrombosis and pulmonary embolism
- poor kidney function.
To find out more about the risks and benefits of these, talk with your GP or specialist.
References
- Dabigatran revisited Best Practice Jnl, Feb 2013
- Dabigatran etexilate New Zealand Formulary v.52 -01 Oct 2016
