Vitamin K.

After a single i.v.-dose of phenprocoumon (0.355 mg/kg) the anticoagulant effect obtained is greater in older than in younger rats. There are no differences between younger and older rats in the rate of elimination, volume of distribution and in the free fraction and free concentration values of phenprocoumon in plasma and liver. After i.v.-injection of 64.3 μg/kg [ ³ H]vitamin K ₁ and different doses of phenprocoumon (0.02 to 3 mg/kg) the [ ³ H]vitamin K ₁ concentration in the liver decreases and the [ ³ H] vitamin K ₁ -2, 3-epoxide concentration increases dependent on the dose and the liver concentration of phenprocoumon. These changes are more pronounced in the older than in the younger rats.