Discrepant In Vivo Recovery of Factor VIII:C Following Infusion of Two Different Monoclonal Factor VIII Preparations

Background: We experienced decreased recovery of factor VIII:C after commercial monoclonal factor VIII infusions. We report the recovery data obtained from infusing two brands of monoclonal factor VIII. Methods: Factor VIII:C activity was measured before and after an infusion of one of two monoclonal factor VIII preparations. The increments were calculated and expressed as a function of units of factor VIII administered per kilogram. Results: Monoclate increments averaged 2.3% (range: 1.6-3.2%). Antihemophilic factor (human) method M (AHFM) yielded an average increment of 1.4% (range: 1-1.7%). Conclusions: The two monoclonal factor VIII preparations used are not equivalent in activity. In switching brands, one must recalculate the prescribed dose based on the institution's experience in recovery of VIII:C from the particular brand to be prescribed. Cost calculations and comparisons should be based on the recovered factor VIII:C increments rather the unit purchase price.