Evaluation of prophylactic replacement therapy in haemophilia B

Prophylaxis replacement therapy was assessed for a period of 12 months in 10 patients with severe haemophilia B showing a high incidence of spontaneous bleeding episodes. Two different schedules of administration of a freeze dried factor IX concentrate were randomly evaluated: according to scheme A, 7.5 U/kg were administered biweekly, whereas scheme B was based on the weekly infusion of 15 U/kg. On prophylaxis the frequency of bleeding episodes was significantly reduced (P <0.005) when compared with that observed in the one year period preceding the trial. Biweekly infusions were superior to weekly infusion (P <0.01), and the benefit appeared to be related to the higher number of days in which measurable levels of factor IX were attained in plasma. Range of motion, which was reduced at the start of the trial in 26 joints was found to have improved in 23. Favourable changes of the joint radiological picture were observed in 6 cases. Hepatitis and factor IX inhibitors did not develop during the trial period. Side effects were rare and mild.