For over 50 years, warfarin has been the drug of choice in preventing AF-related strokes, but a new type of anticoagulant offers more options.
What is an anticoagulant medicine?
An anticoagulant medicine makes the blood take longer to clot. It plays a vital part in helping to prevent strokes specifically caused by atrial fibrillation (AF), which is the most common abnormal heart rhythm in the UK.
AF increases the risk of stroke as it can lead to blood pooling in the heart, which increases the risk of clots forming. If these clots are ejected by the heart, they can block a blood vessel in the brain and cause a stroke.
Warfarin is the most commonly prescribed anticoagulant and, when used appropriately, it’s an effective way of significantly reducing the risk of AF-related strokes. But it requires frequent blood tests and careful monitoring.
What are NOACs and who are they recommended for?
The novel oral anticoagulants (NOACs) are a new class of anticoagulant drug. They can be used in the prevention of stroke for people with non-valvular AF, which is when AF is not associated with a problem in a heart valve. They can also be used in the management of venous thromboembolism, which is when a blood clot forms in a vein. Non-valvular AF is the type of AF that most people in the UK have and, like warfarin, NOACs can help to prevent clots from forming in the first place and help protect you from certain types of stroke.
How many different NOACs are there?
Several drug companies have been involved in the development of the NOACs. In the UK, dabigatran, rivaroxaban and apixaban are currently the ones most commonly prescribed to help prevent strokes in people with non-valvular AF. Edoxaban received its European marketing authorisation in June 2015, though currently very little is being prescribed.
How do they work?
NOACs interrupt part of the complex system involved in the formation of blood clots. This causes the blood to take longer to clot and reduces the risk of AF-related stroke. All of the NOACs have been shown to be as effective at preventing strokes as warfarin. The main difference between NOACs and warfarin is that NOACs are less influenced by diet and other medications.
This means a set dose of a NOAC can be prescribed and the doctor will know that the patient is protected against stroke as long as the drug is taken. This is similar to the way most other drugs are prescribed. In practical terms, this means that the patient does not need to have blood tests to check whether it is working.
Does this mean everyone with AF who is taking warfarin should swap to a NOAC?
No, warfarin is very effective at preventing strokes, and if you’re well controlled on warfarin and are without side effects, then there is no real gain in swapping to a NOAC.
What are the potential side effects?
The side effects depend on exactly which NOAC is being taken; for example, dabigatran can cause stomach upset. As with all anticoagulants, however, a serious complication that can happen is having a major bleed. It’s uncommon, and the chance of having a major bleed with a NOAC is either the same or less than it is if you are taking warfarin. There are several reversal agents available for someone taking warfarin and there is now a reversal agent available for dabigatran (which is for emergency hospital use only). The other NOACs currently have no reversal agent.
The treatment for a bleed will depend on where you are bleeding from and the extent of it. Some signs and symptoms of unusual bleeding can include unexpected bleeding or bleeding that lasts a long time; severe or unexplained bruising, or bruising that gets bigger without a cause; and red or black (tar-like) bowel motions.
You should call your doctor if you have any signs or symptoms of unusual bleeding. If there are signs of internal bleeding or the bleeding is severe, then call 999. Although there is currently no reversal agent for NOACs (besides dabigatran) that can be given, there are specific reversal agents that are in the final stages of clinical trials, and these can completely reverse the effect of NOACs within minutes. However, the anticoagulant effect of NOACs fades rapidly, around 12–24 hours after the last dose.
If you are taking anticoagulant medicine (for example, warfarin or dabigatran) and you suffer a head injury, such as falling and hitting your head, or experience a blow to the head, seek medical help without delay to rule out internal bleeding which may not be immediately obvious.
What happens if you forget to take a dose?
It’s essential that NOACs are taken every day. This is because they act for a much shorter period of time than warfarin, so if you miss a dose, you’re not protected. If you’ve forgotten a dose and it is less than half the time to the next scheduled dose of the drug, take the medicine and continue as normal. If not, take the next dose at the scheduled time. It is important not to take a double dose of the medicine, as that could increase the risk of bleeding.
Are there people for whom NOACs are unsuitable?
If a person has a high risk of bleeding, then oral anticoagulation, including NOACs and warfarin, may not be recommended. There is not enough information about the effects of NOACs in people who take an anticoagulant because they have a metallic heart valve, so it’s not recommended for this group. If you have moderate kidney impairment, NOACs may also not be recommended, as you could be more likely to have a bleed. Your doctor will be able to advise you of what the best option is for you.
Are there any obstacles to them being prescribed?
The main obstacle is that NOACs are more expensive than warfarin, even when the frequent blood testing associated with warfarin is taken into account. Doctors may be less familiar with NOACs, as they have been prescribing warfarin for decades, compared with only a few years for NOACs. With time, NOACs will reduce in price and more doctors will be comfortable prescribing them. Of the 17,000 anticoagulant items dispensed in September 2015 in the United Kingdom, 4,000 were NOAC’s, around 60% of which were Apixaban showing that they are already being more widely prescribed.