Resistance to Activated F IX Concentrate (FEIBA)

Abstract

A 10 yr old hemophiliac with an inhibitor to Factor VIII was treated by repeated infusions of an activated Factor IX concentrate (FEIBA). During therapy the patient was monitored with extensive coagulation studies, and the initial effect of FEIBA on the whole blood coagulation time disappeared in spite of increased doses of concentrate. A fall in Factor IX activity and a rise of antithrombin III and anti-Factor Xa was recorded, while the titer of anti-F VIII remained unchanged. The exact nature of this FEIBA-resistant state was not revealed, but it was speculated that a rise of natural inhibitors of the coagulation system could explain the findings.