dosage
The correct dosage of intake varies even importantly from person to person and, with the passage of time, it can also change for the same individual.
In the case of coumandin it is particularly important to establish the therapeutic dose, since when the dosage is inadequate by default the anticoagulant efficacy is limited, while when it is overdose the risk of bleeding increases considerably.
INR - How to Calculate the Dose
To calculate the correct therapeutic levels of warfarin, doctors use a laboratory test conducted on a patient's blood sample. This survey is called INR (from the International Normalized Ratio) and its results are expressed with a numerical value.
Even before starting the therapy, based on the patient's characteristics and therapeutic needs, the doctor establishes the intervals within which the INR must return. For example, in the case of atrial fibrillation or prevention of venous thrombosis, the correct INR is between 2 and 3, while in patients with mechanical valve prostheses the appropriate INR is a little higher, between 2.5 and 3, 5. Once this interval is established, the therapeutic dose is calculated - and eventually corrected - as long as the blood tests do not show an optimal INR.
It is above all the first days of treatment that are particularly delicate for therapeutic purposes and only through close checks of the INR it is possible to identify the optimal dose for the single person. In particular, when the INR is too high it is necessary to decrease the dosage of coumadin, vice versa when the INR is too low the doses of intake will have to be increased.
- If the INR is lower than required it is necessary to increase the coumandin dose, if the INR is higher it must be reduced
- while if the INR is optimal, the dosage is maintained.
When the INR is particularly high (> 5) the doctor may recommend, in addition to drug withdrawal, the intake of vitamin K orally or intravenously (in the most serious cases) to accelerate the return to the desired values.
Therefore, deciding whether to reduce or increase the dose is solely and exclusively for the doctor; the patient, for his part, must strictly follow the prescriptions.
This also applies in cases where the INR is measured at home, using a device similar to that used by diabetics (analyzes the capillary blood of a finger).
For information purposes we remind you that the tests for calculating the INR detect the so-called " prothrombin time ". In practice they measure the period of time necessary for the formation of a clot after the contact of the blood with appropriate substances. This value, in order to obtain the INR, is then compared with the average prothrombin time of patients not treated with anticoagulants.
In the first days of therapy blood samples to check the INR value are close (every 2-3 days); then, when the stability and the effective dosage have been reached, they pass to a weekly and one every 15-20 days. Based on the INR value detected, the doctor prescribes the dose of medication to be taken until the next check.
When to take it
As a rule, coumadin is taken once a day at the same time, preferably between meals and in the middle of the afternoon (or in the evening before going to bed).
Recruitment Diary
Considering the extreme importance of respecting the right therapeutic doses it is very important to record the individual assumptions on a special diary, together with the INR value provided by the laboratory. In this way the possibilities of error are considerably limited (it is sufficient to cross it when taking the drug on the date of the current day, so as not to run the risk of taking it twice or not taking it at all).
If you miss a dose
If you accidentally skip a dose, this - according to general guidelines - can be taken within a few hours of skipping. On the other hand, if more time has elapsed, the assumption is normally postponed to the following day, during which it is NOT necessary to double the intake (due to the risk of bleeding from overdose).
The error will obviously be marked in the diary and communicated to the doctor.
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