Vitamin K1 and the vitamin K analogues

The use of vitamin K1 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 K1, present in various green vegetables, cereals, seeds, tomatoes, and liver, and vitamin K2 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 K1. This article reviews pertinent aspects of the voluminous literature on vitamin K1 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.