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What is it about ?
Coagulation is a mechanism that allows blood clots to form when blood comes into contact with air or if the blood vessels are damaged. In the event of an injury, the clot causes the bleeding to stop. Unfortunately, a blood clot can also form in the circulatory system and either block a blood vessel where it forms (thrombosis, for example in the leg) or form in the heart (for example in case of fibrillation. ear), get carried into the bloodstream and block a blood vessel elsewhere in the body (embolism). This can cause, for example, a heart attack (infarction), a cerebrovascular accident (CVA), or a pulmonary embolism.
Basically, the body has two systems to clot blood. The first, the platelet system, allows rapid clotting; platelets stick to each other, we speak of platelet aggregation. The clot thus formed is not really solid. To become stronger, it needs protein. These coagulation proteins called ‘coagulation factors’ constitute the second system. The proteins form a network, which firmly binds the clot.
To prevent clotting, we can act on each of these two systems. It is sometimes said that we “thin” the blood, but this is not quite correct. This is because the treatment does not make the blood more liquid, but it prevents the blood clotting mechanisms. It is therefore more correct to speak of anticoagulation and anticoagulants.
In practice, anticoagulation involves two types of drugs: antiplatelet agents and anticoagulants.
Antiplatelet agents
These drugs prevent platelets from sticking together, which slows the formation of blood clots. In Belgium, antiplatelet drugs are
- Acetylsalicylic acid under the brands Aspirin®, Asa®, Asaflow®, Cardioaspirin® and generics
- Clopidogrel under the brands Plavix® and generics
- Prasugrel under the Efient® brand
- Ticlopidine under the brand names Ticlid® and generic
- Cangrelor under the Kengrexal® brand
- Ticagrelor under the Brilique® brand
- Dipyridamole under the brand name Dipyridamole®
- Epoprostenol under the brands Flolan® and Veletri®
- Tirofiban under the brand Aggrastat®
Anti coagulants
These drugs slow down the activity of coagulation proteins. Some are to be taken by mouth (oral anticoagulants), others not (parenteral anticoagulants). The different classes of these drugs are involved at different stages in the production of coagulation proteins:
- Oral anticoagulants, themselves divided into 2 main classes:
- Vitamin K antagonists also called coumarin anticoagulants. Vitamin K indeed plays a role of activator of coagulation, more exactly of certain coagulation factors. Within this class, all products have the same effectiveness, but some take longer to be broken down by the body. In Belgium, vitamin K antagonists are
- Acenocoumarol under the Sintrom® brand
- Phenprocoumone under the Marcoumar® brand
- Warfarin under the brand Marevan®
- Direct oral anticoagulants. These drugs act on other proteins involved in coagulation. In Belgium, direct oral anticoagulants are
- Apixaban under the brand Eliquis®
- Dabigatran under the Pradaxa® brand
- Edoxaban under the brand Lixiana®
- Rivaroxaban under the Xarelto® brand
- Vitamin K antagonists also called coumarin anticoagulants. Vitamin K indeed plays a role of activator of coagulation, more exactly of certain coagulation factors. Within this class, all products have the same effectiveness, but some take longer to be broken down by the body. In Belgium, vitamin K antagonists are
- Parenteral anticoagulants, themselves divided into several classes, including, for example
- Low molecular weight heparins. In Belgium, low molecular weight heparins are
- Dalteparin under the brand Fragmin®
- Enoxaparin under the brand name Clexane®
- Nadroparin under the brands Fraxiparine® and Fradoxi®
- Tinzaparin under the Innohep® brand
- Fondaparinux, under the Arixtra® brand
- Low molecular weight heparins. In Belgium, low molecular weight heparins are
The effect of vitamin K antagonists is monitored by blood tests. Indeed, coagulation must remain within fairly precise limits. This is why clotting time is measured regularly: this measurement shows how long a person bleeds before their clotting system stops bleeding. The test used for this measurement is prothrombin time (PT). The test result is expressed in INR (International Normalized Ratio), an international normalized ratio that indicates the state of coagulation. An INR greater than 2 means the bleeding time is longer (the blood is ‘too liquid’), an INR less than 2 indicates a shortened bleeding time (the blood is ‘too thick’).
Anticoagulation must be well regulated: excessive anticoagulation increases the risk of dangerous bleeding; insufficient anticoagulation increases the risk of blood clots forming.
Vitamin K antagonists are often given in varying doses because everyone reacts to them differently. Some are sensitive to it, others less. A diet rich in vitamin K, which is found especially in soybean oil and Brussels sprouts, can also interfere with the effect of blood thinners. In most cases, however, it is perfectly possible to lead a normal life.
Among the elements that differentiate vitamin K antagonists from direct oral anticoagulants, we find, for example, in addition to their different modes of action, the following:
- There is an antidote if taking a vitamin K antagonist results in a high risk of bleeding or bleeding: vitamin K. For some direct oral anticoagulants, there are currently no products that neutralize the action if there is bleeding, which can be a problem if there is bleeding.
- The effect of vitamin K antagonists should be checked regularly with blood tests. While, for oral anticoagulants, the variations in blood concentrations are less important; they therefore require fewer controls. At the same time, this is also a disadvantage because the doctor does not know exactly how suitable the blood is for the person, and is therefore less able to assess the risk of bleeding.
How often and for how long are blood thinners taken?
In certain situations, for example in certain heart rhythm disorders and certain bleeding disorders, anticoagulants are prescribed for life. In other cases, such as after a blood clot in the leg (deep vein thrombosis or DVT) or pulmonary embolism, they should be taken for several months. The duration of treatment is always determined in consultation with the doctor.
In general, it is advisable to take a dose only once a day, preferably at the same time (in the evening, for example). The dose can thus be easily adjusted depending on the result of the blood test. If you forget to take a dose, you can still take it later in the day. If you have forgotten your medicine for several days or if you have taken more medicine than expected, ask your GP for advice.
What if you have to have an operation?
Any scheduled operation is preceded by consultation with your dentist, general practitioner, specialist and / or anesthetist to determine how best to prepare for the operation. Most of the time, the blood thinner is stopped a few days before the procedure and you are given injections instead. The practical modalities of this management are defined taking into account the type of intervention (minor or major operation) and the risk of bleeding.
In the event of an unscheduled intervention, for example following a traffic accident with bleeding or a fall resulting in a fracture, there are measures to quickly control the coagulation. Report to the emergency services as soon as possible that you are taking anticoagulants.
What can you do ?
Treatment with anticoagulants requires a great deal of discipline.
- Take your medication exactly as your doctor has instructed and strictly adhere to the schedule for blood tests.
- Watch your alcohol intake. In a normal person (without liver disease), two glasses of alcohol a day will not interfere with clotting.
- Certain foods and other medicines can influence the effect of blood thinners. Known examples include vitamin K found in certain foods and supplements, and anti-inflammatory drugs. Always tell your pharmacist, dentist or doctor (general practitioner) that you are taking an anticoagulant. Certain spices and aromatic plants can also influence the effect of blood thinners.
- Profuse or abnormally long bleeding from the gums, spontaneous nosebleeds, wounds that bleed for a long time, large bruises that appear spontaneously after a small blow or a little harsh contact, … may be a sign that your blood is ‘too liquid’. The presence of blood in the urine or stools, the production of black stools and heavy periods are other warning signs.
- Put a note in your wallet or next to your ID card that clearly states that you are taking blood thinners. This information can be vital in some emergency situations such as traffic accidents.
What can your doctor do?
The doctor accompanies you and helps you by giving you the information and advice you need. If your anticoagulant treatment is well regulated, a monthly blood test is sufficient. If the doctor prescribes new medicines or if you develop a new condition, your coagulation will be monitored more closely.
It can always happen that your INR is too high i.e. that your blood is ‘too liquid’. In this case, the doctor may prescribe medicine (a high dose of vitamin K) or, in the worst case, refer you to the hospital. Good self-discipline and good communication with the doctor are essential to avoid coming to such situations.
Treatment with direct oral anticoagulants cannot be monitored with blood tests.
Want to know more?
- Antiaggregants – CBIP – Belgian Center for Pharmacotherapeutic Information
- Oral anticoagulants – CBIP – Belgian Center for Pharmacotherapeutic Information
Sources
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