New Anticoagulants – No More Blood Tests?

 

Anticoagulants are medications that are prescribed to prevent blood clots from forming in blood vessels of the heart. When a blood clot forms in a blood vessel like a large vein in the leg (this is called a deep vein thrombosis), it can block the blood flow, causing swelling and pain. Blood clots can also travel from their original site to other parts of the body, such as the lungs where they can cause life threatening pulmonary embolism.

Although they are referred to as ‘blood thinners’, anticoagulants do not in fact ‘thin’ the blood, what they do is make it more difficult for the blood to form clots.

Anticoagulants are generally prescribed either where a patient has already had a blood clot or where they are regarded as at risk of developing one.

Risk factors include:

have atrial fibrillation (a fast irregular heartbeat)
have a mechanical heart valve
have an inherited blood clotting disorder
have undergone recent surgery such as hip or knee replacement surgery
Of these risk factors, atrial fibrillation is the most common reason for having to take an anticoagulant.

arfarin is the most popular anticoagulant prescribed today, which works by blocking vitamin K – an important part of the blood clotting process. However, Warfarin has two main drawbacks – firstly, you must have regular blood tests to check how quickly your blood is clotting, and secondly Warfarin is affected by certain foods and medications which alter its effectiveness.

Blood tests and visits to the doctor (or a special ‘Warfarin clinic’) are frequent when you are first put on Warfarin, as it’s important that the dose does not lessen the blood clotting process too much, as this can result in bleeding problems. Warfarin must also be taken at the same time every day, and if you miss a dose it’s very important not to take a ‘double dose’ to catch up.

There are now some alternatives to Warfarin that act in different ways and do not have the drawbacks of Warfarin, however they may not necessarily be appropriate in all cases. These new medications are Dabigatran, Rivaroxaban and Apixaban.

Unlike Warfarin they reduce the possibility of blood clots by inhibiting the action of a chemical in the blood called thrombin, which plays a part in the clotting process. Dabigatran actually binds itself to thrombin and stops it working, whereas rivaroxaban and apixaban interrupt the production of thrombin.

Part of the reason for the need for regular blood tests if you are taking Warfarin are due to the effect of certain foods, especially those that have high vitamin K content, such as green leafy vegetables (eg spinach, cabbage, broccoli) and liver, and the effects of some medications including for example an anti fungal ingredient called miconazole and some herbal remedies, such as gingko biloba and ginseng.

None of the three newer anticoagulants are affected by dietary factors. Another advantage of the newer anticoagulants is the speed with which they are effective – Warfarin takes 2-3 days to be effective, while Dabigatran, Rivaroxaban and Apixaban are effective within 2-4 hours.

The new anticoagulants are an option for patients with atrial fibrillation as long as it is non-valvular. Although you do not have to have blood tests with these newer alternatives to Warfarin, you do still need to have regular tests for kidney function. As with all new medications, there is little information on possible side effects of long term use (unlike Warfarin which has been in use for a long time), however current indications are that they are a good alternative to Warfarin for many patients.

NOTE:

This short article deals only with the main points of anticoagulants and there are many factors to consider when deciding which medications are most suitable. You are advised to discuss your individual circumstances with your HeartHealth specialist before making any changes to your medications.

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