Danazol-induced factor VIII and IX bypassing activity in hemophiliacs.

Danazol, a synthetic androgen reported to increase factor VIII and IX activity levels, was given to 6 hemophiliacs. With danazol therapy (600 mg/da) the APTTs shortened by 30-45% of pre-treatment times. However, the activity levels of the deficient factors did not increase significantly nor consistently with the APTT change. The prothrombin times and activity levels of factors XI and XII also did not change during the study period. Addition of plasma from danazol-treated patients to plasma with a known factor VIII inhibitor and to plasma from an untreated severe hemophilia A patient caused a similar shortening of the respective APTTs. Absorption of the danazol plasma with precipitating antibody against factor VIII and IX did not remove the APTT correcting principal. The data suggest that danazol may cause the de novo appearance of an intrinsic coagulation pathway activator having factor VIII and IX bypassing activity.