The clinical importance of parenteral therapy with vitamin K has become well established. The most prolonged improvements in prothrombin clotting time so far reported have followed the intravenous administration of either synthetic vitamin K1 or 2-methyl-1,4-naphthoquinone (menadione). The chemical reactivity and the toxicity of menadione as described by Fieser1 make it less desirable for general use than vitamin K1. A single dose of one of these drugs can restore and maintain normal blood prothrombin levels for periods as long as two or three weeks.2 Some inconvenience is caused by their lack of solubility in water and their sensitivity to ultraviolet rays. This has led to the continued use of water-soluble preparations; the effects of these are of much shorter duration, so that repeated injection is required for prolonged effect.
After the synthesis of vitamin K1, Fieser3 postulated that this light-sensitive vitamin probably did not