Difference between the Novel Oral Anticoagulants (NOACs) vs. CoumadinTM type anticoagulants
Some health problems require a blood "thinning" medication. Atrial fibrillation and mechanical valvular replacements are among those. Blood thinning means that an anticoagulant therapy is prescribed to treat blood coagulation disorders and prevent blood clots from forming.
It is obvious that this has nothing to do with blood density.
Several types of anticoagulants
A great number of medications are used to reduce the body's ability to form blood clots; anticoagulants are among them.
Anticoagulahts are taken as tablets or capsules or given by subcutaneous or intravenous injections. In this article, we will concentrate mainly on oral anticoagulants.
Different types of oral anticoagulants
Oral anticoagulants are divided into two categories: direct oral anticoagulants (DOACs), such as Xarelto™(rivaroxaban), Eliquis™ (apixaban), Lixiana™ (edoxaban), Pradaxa™ (dabigatran), and vitamin K antagonists such as Coumadin™ and Syntron™ (warfarin).
Regular blood tests with warfarin (Coumadin™)
For many years, warfarin was the only existing oral anticoagulant.
Regular blood tests are required to check warfarin's efficacy. The test results the patients receive indicate whether the blood is too "thin" or above normal range, or too "thick", when drug efficacy is suboptimal.
The arrival of DOACs
The arrival of new oral anticoagulants revolutionized the way of monitoring and evaluating the efficacy of these drugs, and regular blood tests were no longer necessary.
People wonder why patients who take DOACs are not required to do as many thorough follow-ups of their condition, such as frequent blood tests, as those who are treated with Coumadin™. This text will shed light on the subject.
An example provides a clearer picture of the blood coagulation system
When you cut yourself, it bleeds. There is a breach in the blood vessels. The body sends a warning signal, like a 911 call. The open wound needs to be closed or an increased risk of haemorrhage may entail. This is similar to blood coagulating.
Let's take a look at the blood coagulation system so as to better understand how anticoagulants work.
Blood clotting proteins
The liver is intimately involved in the coagulation process. It is responsible for the production of proteins that are coagulation factors and part of the coagulation pathway, a cascade of events that leads to the formation of blood clots.
The blood coagulation process may be compared to a game of dominoes with each tile representing a coagulation factor. One of the above-mentioned events is much like the domino effect where a first event sets off a chain of other events.
Coagulation factors are activated one after the other; when the domino effect is over, tiny filaments are produced that cluster together into a thick web. Blood elements, namely platelets and red blood cells, are retained in this web and form a blood clot.
How do anticoagulants work?
Oral anticoagulants are used to hinder the body's ability to form blood clots.
In certain medical conditions, such as mechanical valvular replacements, Coumadin™ is the sole effective medicine while others may be treated with DOACs or CoumadinTM.
Each of these 2 anticoagulants has its own way of working.
On how direct oral anticoagulants (DOACs) work
DOACs inhibit some of the coagulation factors when they are activated and circulating in the blood.
It is as though they were blocking the fall of the dominoes and in so doing they prevent the web of filaments from forming.
DOACs do not interfere with the quantity of circulating factors, but rather with their action, which is more easily predictable than that of warfarin.
Interactions between some medications and DOACs may exist, however, since the DOACs' action is easily predictable, a doctor or a pharmacist may intervene, e.g. by lowering or increasing the dosage of one of these two drugs.
Warfarin, a blood-thinning medication
Warfarin, namely Coumadin™ and Syntron™, works differently from DOACs.It reduces the amount of certain coagulation factors. The net effect is that there are fewer dominoes in the coagulation cascade.
As the number of factors is no longer the same, the end result in the development of filaments that form blood clots is variable.
Warfarin can accomplish the foregoing by linking with vitamin K in the liver, which is responsible for the production of those coagulation factors. The action of the medication is therefore directly related to the amount of vitamin K in the body.
Elements that may interfere
Herebelow is a short list of elements that may interfere with the effect of warfarin on the quantity of filaments that are produced and which contribute to the formation of blood clots.
When only a small amount of vitamin K is available in the body, the effect of warfarin intensifies as the drug has to work with that low amount of the vitamin. Therefore, the production of coagulation factors is for the most part inhibited (blood is too thin).
Whereas when vitamin K exists in a large amount, warfarin is unable to impede the vitamin's action in the production of coagulation factors. Consequently, the effect of warfarin is diminished (blood is too thick).
There are several sources of vitamin K:
- for instance, vitamin K is synthesized partly by some of the bacteria that inhabit the intestine. Any event, such as diarrhea, taking antibiotics, etc., can alter the bacterial flora in the intestine and modify the amount of vitamin K inside the body;
- vitamin K is provided in various healthy foods and mainly in green vegetables. As a person's diet is not the same every day, the effect of warfarin should be expected to vary.
Several drugs may interact with warfarin. At the start or at the end of a treatment or when dosage is modified, the effect of warfarin varies. This is why close monitoring of the situation is of the utmost importance.
Combining prescribed medicine, over-the-counter drugs, natural health and homeopathic products, as well as medicinal herbs can cause interaction and interfere with the effect of warfarin.
Several other factors can hinder the effect of warfarin and cause various damages at different levels. To name but a few, smoking or quitting the use of tobacco, drinking, vomiting, diarrhea or fever, etc.
Efficacy and safety
In short, a great number of factors may exert an influence on the effect of warfarin, while this occurs significantly less often with DOACs. This is why the efficacy and safety of the product should be monitored closely.
By comparing one to the other, the following example will make it easier to understand how 2 anticoagulants can each have its own way of working.
Two roads that head towards a common destination
As mentioned before, these 2 anticoagulants have similar end effects as they are both blood thinners. They aim at reducing the amount of filaments that gather into a thick net, retaining platelets and red blood cells that form blood clots.
However, several factors may affect the action of Coumadin™, which never happens with DOACs; these drugs pursue the same objective but operate differently.
The effect of Coumadin™ and that of DOACs may be compared to two roads leading to a same destination.
The DOACs route
The DOACs' effect is like driving on a paved road, in a straight line, without traffic, on a sunny day.
The car reaches its destination every time without any problem and within the set time frame.
The warfarin route
The effect of Coumadin™ or that of Syntron™ is like going to that same destination, travelling on a road congested with works, on a rainy day.
The car will most likely need to carry on at reduced speed, taking into account the rainfall intensity and the delay due to roadworks. Destination, or in this case CoumadinTM's effect, will be reached, but never at the same time and will vary from day to day.
In other words, the warfarine effect varies from one person to the other.
Vigilance is required
In both cases, destinations and effects will be reached. With DOACs, it will be done within a set time frame while with Coumadin™ the end result will be attained at a variable time.
Anticoagulant Coumadin™ requires continued vigilance on the patient's part because of all the factors that interfere with its efficacy. In keeping with the above road example, we can say that with Coumadin™ one has to be especially mindful of the road signs that are possible interactions.
In summary, unlike with the use of DOACs, several factors have an impact on the effect of Coumadin™. The latter requires regular blood tests in order to check the efficacy and safety of the medication, and adjustment of dosage when necessary.
DOACs do not require blood tests because their effect is stable and is the same from one person to another.
To read: The pharmacology of anticoagulants