Dicumarol therapy. Some effects on platelets and their relationship to clotting tests.

THE CLUMPING of platelets is probably the fundamental stage in the formation of thrombi. It was early demonstrated in experimental animals that administration of Dicnmarol (bishydroxyconmarin; Dicoumarol) in doses adequate to prevent thrombus formation was associated with delay or inhibition of platelet clumping.' ~ Although it may not be necessary to delay platelet clumping in order to prevent thrombus formation, this evidence suggests that it is a relevant factor. In view of this, it would seem important to know the effect in man of Dicumarol and related drugs on platelet behavior. Furthermore, it would be worthwhile to know the relationships between these changes and various clotting tests, in particular those commonly used to control Dicumarol therapy. Quick drew attention to this problem when he wrote, ' ' Obviously, one of the essential needs for the rational use of Dicumarol clinically is an exact study correlating the coagulation time and level of prothrombin with the inhibition of platelet agglutination." Although this point was made 15 years ago and Dicumarol and related drugs have been used extensively, it has received scant attention.