Heparins and vitamin K antagonists (VKA) used commonly are the standard 
treatment of venous and arterial thromboses. They are very efficient and safe, 
but have some limitations: iatrogenicity, laboratory monitoring, parenteral use 
for heparins and fondaparinux. Nowadays, four new inhibitors of factor Xa are 
used orally (rivaroxaban, apixaban, edoxaban, betrixaban), and they are at least 
as efficient as heparins and vitamin K antagonists. The objective is to 
substitute these indirect inhibitors of factor Xa (heparins, low molecular 
weight heparins and fondaparinux) in the prevention of venous and arterial 
thromboembolic episodes. The new direct inhibitors do not require routine 
laboratory monitoring of blood coagulation. They inhibit the extrinsic and the 
intrinsic pathways of blood coagulation. Rivaroxaban and apixaban are 
efficacious and safe in the prevention of cerebral infarcts in patients with 
non-valvular fibrillation. Apixaban is another direct inhibitor of factor Xa 
used orally which is developed in the same indications as rivaroxaban. Edoxaban 
and betrixaban are also in development. The objective of this work is to study 
the pharmacodynamic, pharmacokinetic, the efficacy and safety of these four oral 
direct factor Xa inhibitors.