The preventive effect of Menaquinone-4 (K2) on hypoprothrombinemia caused by Dicumarol in rabbits

Menaquinone-4 (K2), Phytonadione (K1) or vehicle, with Dicumarol and Neomycin, was given to rabbits for 10 days. During this term, prothrombin time and thrombelastogram were observed daily and every other day respectively. Hypoprothrombinemia was definitly caused in rabbits by daily administration of 0.4 mg/kg of Dicumarol intravenously and 200 mg/kg of Neomycin orally, and several deaths due to hemorrhage were observed. In all carcasses, hemorrhage was observed in caecalpart. Under these conditions, the experiments showed that oral administration of K2 or K1 significantly suppressed prolongation of the prothrombin time, and prevented bleeding death of animals. K2 had more potent preventive effect than K1. Both r and k values of the thrombelastogram in rabbits were prolonged after Dicumarol and Neomycin were continuously given, while the groups given K2 or K1 showed no marked effect on the prolongation of r value but apparent suppresive effect on the prolongation of k value until 6 days after the administration. In this case, K2 had significantly more potent suppressive effect than K1.