Hi I Am Prescribed 100 Mg X 2 Of A

Hi I am prescribed 100 mg x 2 of a medication in capsule form light green and white with G24 on it. The name starts with a z. I had a TBI 9 years ago and was recently prescribed this medication for headache and sudden onset of seizures. I need to know the side effects, because I am having daily headaches that turn to migraines and seem to worsen after taking the medication. I have also still been having Grand Mal Seizures. I see my neurologist on the 25th of this month and was on the medication from 1/25 at 100 mg per day and then upped to 200 mg per day after that.