Anticoagulant therapy is indicated when there is danger of clot formation within a blood vessel.
Conditions in which anticoagulant therapy is employed include occlusive vascular disease, such as coronary artery occlusion, cerebrovascular and venous thrombosis, and pulmonary embolism. It is administered prophylactically when major surgery is planned for a patient with a history of arterial stasis, and for patients who must be immobilized for a prolonged period of time. A third group of anticoagulant agents, the antiplatelet agents, are effective in preventing a primary step in the formation of thrombi, that is, the clumping together of platelets, especially in the cerebrovascular system. These agents are classified as antithrombocytics and are not to be confused with or used as a substitute for other types of anticoagulants. The major difficulties that may arise during the course of anticoagulant therapy are hemorrhage and drug interaction.