Hepatic enzyme induction and vitamin K1 elimination in man.

We have studied the effect of hepatic enzyme induction on vitamin K1 elimination in patients on long-term anticonvulsant therapy and in volunteers given rifampicin. Neither the anticonvulsants (phenytoin and phenobarbitone) nor rifampicin had any significant effect on vitamin K1 elimination half-life or AUC. The neonatal haemorrhage which occurs in babies born to mothers on long-term enzyme inducing drugs is unlikely to be related to an increased rate of vitamin K elimination in the mother.