Effect of treatment with activated prothrombin complex concentrate (FEIBA) on factor VIII-antibody level.

The influence of treatment with an activated prothrombin complex preparation (FEIBA) on the antibody level was studied in 10 haemophiliacs with an antibody to factor VIII. The antibody level was observed to rise at least once in five patients, while in the remaining five patients no rise occurred. In all, 6 out of 31 treatments were followed by an anamnestic rise of the antibody level, corresponding to 19.4%. A rise of the inhibitor level following FEIBA treatment is likely to occur in patients who show a marked antibody rise after factor VIII treatment (good responders), but have a low antibody level at the time of treatment. High doses of FEIBA and simultaneous of red cells may also enhance the likelihood of an anamnestic response. Stimulation of antibody production is probably due to the presence of small amounts of factor VIII in this preparation.