A good friend of mine had a serious seizure. How well does medication prevent further seizures?

My good friend Lana called me this morning from the hospital. She had a huge seizure last night she doesn’t recall but her husband said it scared him to death as she was screaming and jerking her entire body and bit her tongue badly. How well can medication keep this from happening again since she has had fairly frequent mini strokes for a year? She is 75.