Toxic effects of the vitamin K family are manifested mainly as hematologic and circulatory derangements. Not only is species variation encountered, but profound differences are observed in the ability of the various vitamin K compounds to evoke a toxic response (Barash, 1978). The natural forms of vitamin K, phylloquinone and menaquinone, are nontoxic at very high dosage levels. The synthetic menadione compounds, however, have shown toxic effects when fed to humans, rabbits, dogs and mice in excessive amounts. The toxic dietary level of menadione is at least 1,000 times the dietary requirement (NRC, 1987). Menadione compounds can safely be used at low levels to prevent the development of a deficiency but should not be used as a pharmacologic treatment for a hemorrhagic condition. In studies with chicks, the major effect of toxic levels of menadione was a high mortality rate (NRC, 1987).
