Synonyms in a broader sense
Phenprocoumon (active ingredient name), coumarins, vitamin K antagonists (inhibitors), anticoagulants, anticoagulantsThe drug known under the trade name Marcumar® contains the active ingredient phenprocoumon, which belongs to the main group of coumarins (vitamin K antagonists). The coumarins are molecules that have a suppressive effect on the natural processes of blood coagulation and thus inhibit the coagulation of the blood (blood coagulation inhibitors). The exact dosage must be determined individually for each patient by the treating physician.
For this purpose, the so-called thromboplastin time must be determined before the actual start of treatment. Throughout the entire intake phase, this time is checked at regular, close intervals and the drug dosage is adjusted if necessary. The Quick- and INR-values also provide information about the body’s own ability to clot blood.
The INR value is an international measure for the evaluation of blood coagulation. High values mean that the clotting time is longer than the standard value and the bleeding tendency is correspondingly high. A low value, on the other hand, indicates a shortened coagulation time and an associated increased risk of thrombosis.
In principle it can be said thus that blood-clotting restraining medicines such as Marcumar® increase the INR value and lower thus the danger of the Thrombenbildung. At the beginning of drug administration, it is likely that the patient’s coagulation values fluctuate very strongly, which makes regular monitoring and adjustment of the dosage all the more necessary. According to some experts, the reason for this is the fact that a therapy with Marcumar® is usually initiated with a comparatively high dose of the drug.
The patient is encouraged to take up to 8 tablets within 24 hours in the first two days. However, this information varies from patient to patient, which is why both the initial dose and each additional dose must be determined by the treating physician and must be adhered to by the patient. Due to this comparatively high intake dose, the INR value can increase enormously in the first few days (values above 3.0) and thus the blood clotting ability can decrease accordingly.
There is an apparently increased risk of bleeding, the probability of developing a thrombosis apparently decreases. However, an increased INR value at the beginning of treatment is not a serious measure of actual blood clotting. This is due to the fact that one of the coagulation factors (factor VII) influenced by Marcumar® has a low plasma half-life of only 5-6 hours.
For this reason, only the concentration of this one vitamin K-dependent coagulation factor decreases after the initial intake of Marcumar®, while factors II, IX and X remain fully active in most cases. For some of these factors, the plasma half-life is up to 60 hours. Since these coagulation factors are also much more important for blood coagulation, this is referred to as an apparent increase in the INR value.
The doctor will check the coagulation values after a few days and reduce the drug dose again. The further daily dose to be taken depends on the determined values. If the INR value is below the target value for the patient (the target value is usually an INR of 2-3.5), a daily dose of one and a half tablets (approx.
4.5 mg of the active substance) is recommended. However, if the INR value determined in the control examination is within the target range, usually only one tablet (about 3 mg phenprocoumon) should be taken over 24 hours. If the coagulation value is too high (from 3.5), the maximum daily dose must be reduced.
In this case, the attending physician usually prescribes the intake of half a tablet of Marcumar (i.e. 1.5 mg). If an INR value of more than 4.5 is reached, the drug application must be suspended for the time being. This list is intended to make clear how dependent the maximum daily dose must be on the measured blood coagulation value.
As a rule, after a “trial period” only a so-called maintenance dose of approximately half to one and a half Marcumar tablets per day is administered. After the treated patients have been adjusted accordingly, the INR value moves within a relatively constant measuring range.Nevertheless, even after the target value has been reached, blood coagulation must be checked regularly, usually every three to four weeks, and the drug dosage adjusted if necessary. While taking the tablets, the treated patient should make sure that the Marcumar tablets are always taken at about the same time (preferably in the evening).
The medicine must be swallowed whole, with sufficient liquid. After discontinuing Marcumar, it may take another 10 -14 days before the anticoagulant effect disappears and the normal coagulation process can take place again. This fact can be explained by the fact that only after this time can a sufficiently high concentration of fully activatable coagulation factors be formed. In emergency situations, it is therefore necessary to supply the missing coagulation factors II, VII, IX and X to the organism from outside in order to reduce a possible risk of bleeding. Also in connection with planned operations and dental treatments, it must always be remembered to discontinue the anticoagulant drug early enough and thus prevent an increased bleeding tendency.
