The Dr is most probably using Topamax as a mood stabilizer. Many of the seizure meds such as Depkote, Topamax, Trileptal and Lamictal are used as mood stabilizers. It is used alone but more typically as adjunct with antipsychotics. He could also being using it for weight loss (since you had said he gained weight on the Seroquel). Topamax causes signifcant weight loss esp in higher doses. Has he been diagnosed with a mental illness? The meds you mention are quite typical for many addict patients I have cared for.