What Are The Uses And Side Effects Of Dilantin?

My husband has been taking Dilantin since the 14th of this month as he had had his first grand mal seizure on the 13th. He was taking 4 pills a day but his doctor switched him to 3 a day. He's been doing relatively good on it but today he took his 1st pill on an empty stomach, felt sick so he at an apple, threw up, felt better. Was fine for a few hours then threw up again. Was fine for the rest of the day then after eating dinner took his next 2 pills, had heartburn, took tums and it went away. He's also been having these nasty smelling burps. Is this something we should be concerned about?