Could Interaction Between Dilantin And Eliquis Cause The Need To Increase Dilantin Dosage After 40 Years Of This Medication Intake?

I have taken dilantin for 40 yrs. The past 2 years I have also been on eliquis. Now my blood level for dilantin shows I need to take 300 mg instead of 200 mg. I am suspecting that this interaction between the 2 drugs is the problem. Otherwise, I have no concerns.