How Well It Works
If you have a bleed, the infusion of clotting factors stops bleeding within hours, although the exact amount of time varies. Heavy bleeding takes longer to control than light bleeding. If the proper amount of clotting factors is given, bleeding will stop normally.
Clotting factors can prevent bleeding when they are given before a procedure, surgery, or an activity that has a high risk of causing a bleeding problem.
If you get clotting factors on a regular schedule to prevent bleeding, you likely will have fewer bleeding episodes. You might also have a lower risk of problems linked to bleeding. These problems include long-term damage from repeated bleeding into your muscles or joints.
Source: http://www.webmd.com