The effect of an injectable progestogen contraceptive on blood coagulation and fibrinolysis.

In 26 women receiving either medroxyprogesterone acetate (Depo-Provera) injections or combined oestrogen-progestogen pills for contraception, tests of coagulation and fibrinolysis were performed before treatment, and after 8, 16 and 24 weeks of therapy. In the medroxyprogesterone group no significant changes were induced in fibrinogen, the vitamin K-dependent factors, or antithrombin III. Plasminogen levels fell during therapy, and were significantly lower than pre-treatment values after 16 and 24 weeks. By contrast, the 13 women receiving oral contraceptives showed raised levels of fibrinogen and plasminogen after 8 weeks of treatment, and of factors VII and X after 24 weeks. These data suggest that medroxyprogesterone acetate injections induce fewer changes in the blood coagulation system than oral contraceptives.