I Have A Patient That Has A Very Bad Seizure

I have a patient that has a very bad seizure disorder and is also schizoaffective. She is on Dilantin and was recently hospitalized for suicidal ideation and put on Lithium against my request. I know this combo increases lithium toxicity. She was put on 600 mg daily of lithium should I reduce that? She is on Dilantin 200 mg BID.