Clinical Experiences with 4-Hydroxycoumarin Anticoagulant No. 63 and the Antagonistic Effect of Menadione and Vitamin K ₁

The successful use of dicumarol in the prevention of intravascular thrombosis and subsequent embolism has led to the investigation of other coumarin compounds as therapeutic anticoagulants. 4-Hydroxycoumain anticoagulant No. 63 is such a compound. Like dicumarol, it induces hypoprothrombinemia and daily tests of prothrombin time are necessary as a guide to dosage. Our experience indicates that a less fluctuating and somewhat more consistent therapeutic hypoprothrombinemia can be established and maintained with anticoagulant No. 63 than with dicumarol. The potential disadvantage of the prolonged hypoprothrombinemia after administration is stopped is counter balanced by the strong and relatively rapid antagonistic effect of vitamin K 1 .