Summary
Due to large inter-individual variations, the dose of vitamin K antagonist required
to target the desired hypocoagulability is hardly predictible for a given patient,
and the time needed to reach therapeutic equilibrium may be excessively long. This
work reports on a simple method for predicting the daily maintenance dose of fluindione
after the third intake. In a first step, 37 patients were delivered 20 mg of fluindione
once a day, at 6 p.m. for 3 consecutive days. On the morning of the 4th day an INR
was performed. During the following days the dose was adjusted to target an INR between
2 and 3. There was a good correlation (r = 0.83, p<0.001) between the INR performed
on the morning of day 4 and the daily maintenance dose determined later by successive
approximations. This allowed us to write a decisional algorithm to predict the effective
maintenance dose of fluindione from the INR performed on day 4. The usefulness and
the safety of this approach was tested in a second prospective study on 46 patients
receiving fluindione according to the same initial scheme. The predicted dose was
compared to the effective dose soon after having reached the equilibrium, then 30
and 90 days after. To within 5 mg (one quarter of a tablet), the predicted dose was
the effective dose in 98%, 86% and 81% of the patients at the 3 times respectively.
The mean time needed to reach the therapeutic equilibrium was reduced from 13 days
in the first study to 6 days in the second study. No hemorrhagic complication occurred.
Thus the strategy formerly developed to predict the daily maintenance dose of warfarin
from the prothrombin time ratio or the thrombotest performed 3 days after starting
the treatment may also be applied to fluindione and the INR measurement.
