The use of non-activated prothrombin concentrate in the management of haemophilia A with factor VIII antibodies.

Three children with haemophilia and antibodies to factor VIII were treated with a non-activated prothrombin concentrate (Prothrombinex) for 12 bleeding episodes. There was clear clinical response and joint aspirations were performed after infusions of phothrombinex in a dose of 30--50 factor IX units/kg body weight and there was no clinical evidence of thrombosis or febrile reactions. There was a significant shortening of the activated partial thromboplastin time (PTT) at one and four hours after the initial infusion with a return to pre-infusion levels 9--24 hours after infusion. The shortening in the PTT was less marked in subsequent infusions. There were no changes in the level of factor VIII procoagulant activity, factor VIII related antigen or factor VIII antibodies after the infusion. In two patients platelet function studies were unaltered by the infusion and in one patient procoagulant levels of factor II, IX and X were no greater than expected from the infusion. We conclude that infusions of non-activated prothrombin concentrates are clinically effective in the treatment of children with haemophilia and factor VIII antibodies but the mechanism of action is unknown.