Drug Interactions With Phenytoin
Vitamin DPhenytoin may make vitamin D less effective. People taking phenytoin may need extra vitamin D. Ask your healthcare provider if you need supplementation.
Warfarin and phenytoin may interact unpredictably, perhaps increasing or decreasing the risk of bleeding. This combination may also increase the risk of phenytoin side effects. Check with your healthcare provider before taking these medications together, changing your dosage of either of these medications, or stopping either of these medications (if you had been taking them together).