Respiratory pharmacology. Antithrombotic and fibrinolytic therapy.

Antithrombotic therapy with heparin is effective in reducing the incidence of thromboembolic disease when given prophylactically to high-risk patients. Heparin followed by oral antithrombotic therapy is accepted practice for the management of established thromboembolism. Fibrinolytic therapy has been demonstrated to be effective in recanalization of vessels occluded by thrombus, but is contraindicated if the effect of peripheral embolization from the occlusion is likely to result in severe morbidity. The use of heparin and oral antithrombotic drugs is associated with an increased frequency of bleeding, and requires careful clinical and laboratory control, for which the best methods have not yet been determined. Low-molecular-weight preparations of heparin have been shown to have effectiveness when administered once or twice a day, but not to have less risk for hemorrhage than regular heparin. Fibrinolytic therapy is entering a new phase with the conclusion of clinical trials of the newer agents that are associated with a reduced risk of systemic anticoagulation.