Vitamin B6, B9 & B12 Folic Acid
ModerateThe leaflet says that folic acid taken together with phenytoin may make phenytoin work less well. Vitamin B6, B9 & B12 and Folic Acid are both named here, but the text gives no separate effect for this pair beyond that.
These medicines are often taken together with some care. Your doctor may change a dose, space them apart or check on you more often. Make sure your doctor and pharmacist know you take both.