Lab tests show that Dutasteride (Urodart) does not push Phenytoin off the proteins in the blood that carry it around. Phenytoin also does not push Dutasteride off. So the two medicines do not get in each other's way in this respect.
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.