AS ORAL anticoagulant therapy has become more widespread the hazard of associated bleeding has increased; today bishydroxycoumarin (Dicumarol) and similar preparations are common causes of drug intoxication.1 This serves to emphasize the importance of effective antidotes to combat hypoprothrombinemia so induced. The comparative effects of oil-soluble vitamin K1 and the water-soluble vitamin-K-like preparations (synthetic naphthoquinones) in correcting such hypoprothrombinemia is the subject of this paper. Their relative effectiveness in correcting prothrombin deficiency due to other causes is also discussed.
Dam first described a deficiency state in the chicken similar to scurvy, not prevented or cured by ascorbic acid, characterized by a marked prolongation of the clotting time, which he ascribed to a lack of a particular antihemorrhagic factor—vitamin K, which was fat-soluble.2 Subsequent work by Quick and his group established the relationship of vitamin K deficiency and hypoprothrombinemia. In 1939 Fieser synthesized vitamin K1, identical with