The administration of anticoagulants.

Heparin is administered parenterally. Its therapeutic effect is measured by the clotting time of the whole blood, determined by the method of Lee and White. An excessive anticoagulant effect is controlled by the administration of specific antagonists, toluidine blue or protamine sulfate. Dicumarol* is admintered orally in amounts sufficient to reduce the prothrombin activity of the plasma to between 10 and 30 per cent of normal. The prothrombin time, which represents such a reduction in prothrombin activity, will vary according to the method by which the determination is performed, the thromboplastin used, and the technique followed. Excessive prolongation of the prothrombin time is antagonized by the administration of vitamin K in large doses. Long-term therapy with Dicumarol is sufficiently hazardous to require considerable experience on the part of the physician. Where an immediate anticoagulant effect is necessary, yet prolonged administration anticipated, combined therapy with both heparin and Dicumarol may be used until the prothrombin time is prolonged satisfactorily, whereupon heparin may be discontinued.