I Went To A Free Clinic Today And Was Prescribed

I went to a free clinic today and was prescribed Dilantin, I feel like the nurse practitioner hurried her diagnosis. I have bipolar disorder, and I take Trazadone Paroxatine, and bispurone for it. She wanted me to take Dilantin for anxiety and mood stabilization. My concern is that I am a writer and the side effects mentioned have to do with slow thought processing slurred speech etc. She prescribed 100 mg per day. Will this dosage cause any disorder in my thinking? or reactions?