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.
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.
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.
Contact your healthcare provider urgently if these things happen to you:
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).
Precautions - before starting anticoagulants
Are you pregnant?
Do you have or have you had a stomach ulcer?
Have you had a bleed into the brain (a haemorrhagic stroke)?
Are you going to have major surgery?
Do you have very high blood pressure?
If so, it’s important that you tell your doctor or pharmacist before you start anticoagulants. Sometimes a medicine isn’t suitable for a person with certain conditions. Your doctor will talk to you about the benefits and risks of taking anticoagulants.
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.
Credits: Sandra Ponen, pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland
Last reviewed: 05 Aug 2018
Anticoagulants for atrial fibrillation
Deciding between warfarin, dabigatran and rivaroxaban
Until 2011, the most commonly prescribed oral anticoagulant in New Zealand was warfarin (known by the brand names Marevan and Coumadin). Since then, new oral anticoagulants have become available, such as dabigatran and more recently rivaroxaban.
These medicines work well at reducing the risk of blood clots, but they are slightly different.
Once it has been decided that you need anticoagulant treatment, discuss the best option with your doctor.
The following are some of the key points to discuss with your doctor and pharmacist to help you choose the anticoagulant most suitable for you and your situation.
Anticogulants: help me choose
Situations when warfarin may be preferred to dabigatran and rivaroxaban
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. Treatment with warfarin is normally long term.
Dabigatran: You will take 1 dabigatran capsule twice a day. You will most likely stay on the same dose all the time. Treatment is usually long term.
Rivaroxaban: You will take 1 rivaroxaban tablet once a day. You will most likely stay on the same dose all the time. Treatment is usually long term.
Will I need regular blood tests?
Warfarin: For the first few weeks and months, you will need frequent blood tests. 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 occassional tests to check your kidneys and liver.
Will I have to change what I eat or drink?
Warfarin: This medicine interacts with alcohol and many common foods. Major changes in what you eat may affect how your body responds to warfarin. Avoid drinking cranberry juice and 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 about side effects?
All anticoagulants have side effects and can cause bleeding and bruising. Other common side effects include:
Warfarin: diarrhoea (runny poos), nausea (feeling sick), hair loss
Rivaroxaban: nausea (feeling sick), indigestion, tummy cramps and headache.
What about the risk of bleeding?
All anticoagulants have a risk of bleeding but, as compared with warfarin:
Dabigatran has more risk of stomach bleeding but less risk of bleeding in your brain (intracranial bleeding)
Rivaroxaban has more risk of stomach bleeding but less risk of bleeding in your brain.
What happens if I need non-urgent surgery, including dental surgery?
It is important to tell anyone treating you, including your dentist and physiotherapist, that you are taking an anticoagulant. You should tell them well before your appointment.
Warfarin: You would usually stop taking warfarin about 3 days before planned surgery, depending on the type of surgery, and start taking it again straight away afterwards. You would not usually need to stop taking warfarin before dental surgery, but your blood clotting would be tested to help decide. Ask your dentist for advice.
Dabigatran: You would usually stop taking dabigatran for 12 to 48 hours before planned surgery or dental treatment, and start taking it again soon after the surgery, but check with your doctor or dentist first.
Rivaroxaban: You would usually stop taking rivaroxaban for 24 to 48 hours before planned surgery or dental treatment, and usually start taking it again soon after the surgery, but check with your doctor or dentist first.
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.
For more information visit the