Vitamin K1 and the vitamin K analogues

The use of vitamin K 1 and various preparations with vitamin K activity in the treatment of hypoprothrombinemic states has long been a well‐established procedure. Because the K analogues have often been popularly referred to as vitamin K, confusion has arisen regarding the relationship between these compounds and the true vitamin K. Two types of vitamin K have been found in Nature: vitamin K 1 , present in various green vegetables, cereals, seeds, tomatoes, and liver, and vitamin K 2 isolated from putrefied fish meal. The former has been synthesized and represents the commercially available form of the true vitamin. The K analogues were originally synthesized in an attempt to find compounds with more potent antihemorrhagic activity or substances which could be administered more easily than the early preparations of vitamin K 1 . This article reviews pertinent aspects of the voluminous literature on vitamin K 1 and the K analogues and presents the recorded differences (or similarities) in effectiveness and toxicity between the two types of compounds in various clinical states.